CHAPTER I.

HELP-HUDSON!

"Try him again, Frank! He ought to answer any minute."

"It's eleven o'clock. He's probably in bed and asleep."

"Try him once more."

"All right, but I'll bet we don't get him. Chet Morton wouldn't stay up this late. You know how he likes to sleep."

Frank Hardy again turned to the short-wave radio that he and his brother Joe were licensed to operate on amateur frequencies. For half an hour the boys had been trying to contact their chum, Chet Morton, also a qualified radio operator. It had been Chet's idea that the Hardys fix up their short-wave station for push-to-talk operation. Chet had assured them that he, too, would be on the air that night with his set rebuilt the same way.

"K2XOB, K2XOB, from K2XEJ," droned

Frank, then removed his finger from the transmit button on the microphone and looked up. "Chet's probably forgotten all about it. We may as well give up." With his finger away from the button switch, the receiver turned on automatically.

"Wait a minute," said Joe, retuning the receiver dial. "This is Chet!"

"K2XEJ, this is K2XOB." The familiar voice of the stout friend of the Hardys filled the room. "Had an errand to do for my Mother, hope you haven't been waiting long."

"Just about wore out our transmitter trying to raise you," Frank replied.

There was an awful squeal from the receiver. Then Chet's voice came through again.

"Mother asked me to go and look at a bunch of stuff that's to be sold at auction tomorrow afternoon."

"Hope you had a nice evening," said Joe dryly.

Another shriek issued forth. "I'd have been bored stiff if it hadn't been for the stuffed animals," answered Chet. "All kinds of stuffed animals. And a full set of taxidermy equipment."

"Taxi equipment!"

"Taxidermy-taxidermy, not taxi. The process of making dead animals look like live ones. A fellow could start up in business for himself with a set of those tools. I'm kind of interested to try it."

The Hardy boys glanced at each other in astonishment. It was not often that happy-go-lucky Chet Morton showed such enthusiasm over any subject not connected with food or sleep.

"I have a secret to tell you," said Chet.

"What is it?" Frank asked.

"I said it was a secret. Think I'm going to spill it over the air? I'll let you in on it tomorrow if you'll come to the sale with me."

Frank and Joe saw little prospect of any excitement at an auction sale, but Chet's promise to tell them a secret was intriguing. Also, they were more than a little puzzled by his sudden interest in taxidermy. Their stout friend did not wait for any further argument.

"See you at the Suydam mansion tomorrow afternoon-half-past two sharp. I'm signing off now. So long, fellows."

He was gone.

"Well, what do you know!" exclaimed Joe. "Chet seemed pretty excited."

"By tomorrow afternoon he'll probably have forgotten what he was excited about," laughed Frank, turning off the transmitter. "I guess we may as well go to bed. Aunt Gertrude will be up here in a minute wanting to know why we 're still awake."

Joe fumbled idly at the receiving set, tuning it to various frequencies. Suddenly, on one of them, the boys heard a faint voice:

"Help!"

"Listen!" gasped Joe. He pressed his ear close to the receiver. "Did you hear that?"

For a moment there was silence. Then they heard the voice again-this time little more than a whisper.

"Help!" It was followed by a confused roar of static, through which they heard a word that sounded like "Hudson." That was all.

"Help-Hudson," muttered Frank, frowning. "What do you make of that?"

"Sounded like someone in trouble."

"There'll be someone else in trouble mighty soon if you two boys don't turn that thing off and get into bed pretty quick," broke in a strident voice. "How can a body sleep with such a racket going on?"

The boys leaped up guiltily. There, at the head of the attic stairs, stood their Aunt Gertrude. Clad in a voluminous purple flannel dressing gown, with her hair done up in curlers which projected stiffly from her head, she was an awe-inspiring sight. Mr. Hardy's sister was keeping house in the absence of Mrs. Hardy, who had gone away for a visit, and she took her responsibilities very seriously.

"Bed!" she said crisply. "And no more keeping folks awake."

"Yes, Aunt Gertrude," said her nephews meekly, and hastily turned off the radio.

They trailed their aunt down the stairs. She Was muttering wrathfully.

"If you want to listen to the radio, what's the matter with the one in the living room? Plenty of good programs on that. But no, you 'd rattier sit up in a stuffy old attic with that screechy set. I declare, I'll never understand boys."

The brothers hardly had reached the landing before they heard a door open downstairs. This was followed by a familiar shout echoing in the lower hall.

"Everyone asleep?"

"It's Dad! "Frank cried.

"With whoops of delight the two boys rushed down the stairs to greet their father.

"Now wait a minute!" said Aunt Gertrude. "You don't have to act like wild Indians just because your father is back."

But the boys paid no attention. Already they were halfway to the lower hall. Their father, the noted detective Fenton Hardy, had been away from home for several days on business in connection with an important case. Frank and Joe were curious about it, but he had not confided in them as yet, and they knew better than to ask questions.

"Well, boys! I was afraid you'd be in bed," he smiled, as Frank helped him take off his overcoat.

"We were just going to bed," said Frank, catching Aunt Gertrude's eye.

"And still are," she told them firmly from the stairs. "Sitting up till all hours listening to a screeching radio in the attic."

"Oh-the short-wave set!" exclaimed Fen-ton Hardy. "That reminds me. This case I'm working on--"

"Yes?" said Joe eagerly.

The boys were disappointed. Under the stern eye of Aunt Gertrude their father had changed his mind about telling them of the mystery.

"Funny," said Joe to Frank, before they fell asleep, "that call we heard-'Help-Hudson.' "

"Yes, but I'm more interested in what Dad's going to tell us."

The next morning after breakfast Fenton Hardy led his sons to his car and unlocked the trunk compartment.

"I'll need a little help unpacking this," he said, indicating a bulky box. "You boys know about radio sets. Can you uncrate it?"

"It's a new radio set?" asked Frank.

Their father nodded. "Yes, it is the latest all-band short-wave transmitter-receiver unit designed for the government."

"Why did you get it?" asked Joe, opening the tool box for a hammer and screw driver.

Fenton Hardy sat down on a bench. As his sons uncrated the set, he explained the radio and his need for it. "You see, I have authority to transmit on state police channels, the Bayport police and others. This unit is pre-tuned for police channels, a flick of the switch shifts tuning. A variable frequency feature permits its use on amateur bands. And you boys hold the needed licenses to operate on all these channels."

The celebrated detective then told of his newest case, dealing with a series of thefts of valuable radio equipment in various parts of the country and how he hoped the new radio would help solve it. equipment in various parts of the country.

"It's a tough assignment, although it might be solved in an armchair," he said mysteriously.

"How could you solve any mystery sitting in an armchair?" asked Frank in bewilderment.

"Well, there are no clues to the identity of these thieves as yet. And there are no clues to the place where they may be hiding the stolen goods, either. But all these thefts involve radio equipment, and they've taken place in so many scattered parts of the country that I have an idea the crooks may be communicating with one another by radio."

"By short-wave!" exclaimed Frank.

"Perhaps. That's why I bought this special set. If the thieves are using short-wave, we may be able to pick up some of their messages. If we do, we may be able to track them down without moving out of the house."

"That would be an armchair case," agreed Joe. "Let's get this radio uncrated and set up so we can start work."

"I can't give you much to go on," said Fen-ton Hardy. "If you hear any messages that seem to deal with radio equipment, keep your ears open. This Hudson gang--"

The boys turned, startled.

"Did you say Hudson gang?" cried Joe.

"That's the outfit I suspect. But I haven't any proof," replied their father.

"Why, gosh, we heard that very name on short-wave last night!" Frank said.

It was Mr. Hardy's turn to be startled. His sons told him about the strange call they had picked up after their talk with Chet. The detective was deeply interested, although he was of the opinion that it might have been a mere coincidence. Frank and Joe were firmly convinced, however, that they had stumbled on a valuable clue.

The boys lost no time in uncrating the radio outfit and installing it in their father's study. It was a strong, compact set of the latest type, with so many improvements that it made their other radios look old-fashioned. It had a wide range and great selectivity.

The boys spent the rest of the morning listening to short-wave signals and fragments of messages, both regular and in code. But they did not hear the name "Hudson" again.

"We'll keep trying," said Frank to Joe after lunch. "If we hadn't promised to meet Chet at the Suydam mansion -- "

"Golly, I'd almost forgotten about Chet. We'd better hurry. Remember, he said he'd tell us a secret. Let's go."

Lunch had been late, and the Suydam mansion was on the outskirts of the city, on the other side of Bayport from the Hardy home. It was well after two-thirty when the boys arrived at the place.

The auction already was in progress on the front lawn of the rambling old stone house. A crowd of several hundred people had gathered there. The Hardy boys had difficulty in finding Chet Morton.

"And now what am I bid for this magnificent stuffed owl?" bellowed the auctioneer, as his helper exhibited a moth-eaten bird that once had been white.

"Twenty-five cents!" chirped a voice from somewhere in the front rank of spectators.

"Twenty-five cents!" exclaimed the auctioneer reproachfully. "Surely, young man, you are not serious. Why, this specimen is worth much more."

"Seventy-five!" shouted a man in the middle of the crowd.

"One dollar!" called out another.

The Hardy boys had recognized the voice of the twenty-five-cent bidder as that of Chet Morton. As they made their way toward him, they heard him offer a dollar and thirty cents for the owl, but he was immediately outbid. By the time the brothers reached their fat friend's side, the bird had been sold for two dollars, but not to Chet.

"Hello," said Frank, seating himself beside his friend. "Say, what do you want with a stuffed owl?"

"Never mind. Tell you later. Help me bid," whispered Chet urgently. "What kept you so late? Gee whiz, if you 'd been here, I might have bought that owl. Look-there's a leopard skin.

I've got to have that. One dollar!" he roared, as the auctioneer held up a black and yellow spotted skin rug.

"Two!" shouted a man back in the crowd.

"Those fellows have been bidding against me all afternoon," groaned Chet.

"Three!" cried Frank. And to Chet he said, "What on earth do you want with a leopard-skin rug?"

"Never mind. Keep bidding!"

But, although Joe and Frank rallied to their chum's assistance and bid to the limit of the money in their pockets, the leopard skin went to a hard-looking individual.

Old Mr. Suydam, deceased owner of the mansion, had been something of a sportsman in his day, and one whole room of his large home had been filled with trophies of the hunt. There were stuffed birds and moose heads, tiger skins and buffalo hides. Chet did win out in the bidding for a handsome specimen of stuffed skunk, for which the hard-looking man made no offer.

Only one other time were the boys successful. That was when they bought a stuffed bear for fifteen dollars. As Chet stepped up to pay for it, the auctioneer handed him a slip of paper with a number on it.

"Pay me after the sale," he said. "I'm too busy to bother with money right this minute. And now, ladies and gentlemen ..."

The Hardy boys thought this a very unbusinesslike procedure, but the man seemed to know what he was doing. They noticed that the hard-looking customer who had outbid Chet had claimed the skins and specimens as soon as he had bought them.

Suddenly Joe nudged his brother. "Look!" he said, indicating a car at a little distance. "That driver is loading up all those skins and specimens the other man bought-and they haven't been paid for yet."

Frank looked up just in time to see the fellow at the car toss the leopard skin into the back and close the door. He jumped into the front seat and the car began backing out of the driveway. Absorbed in the auction, no one in the crowd but the Hardys had noticed the incident.

The hard-looking man who had been bidding against Chet quietly slid out of his seat, made a dash for the automobile, and jumped in. It roared away.

"They're stealing that stuff!" whispered Frank to Joe. "Come on! After them!"

CHAPTER II.

CHET, THE TAXIDERMIST.

By the time the Hardy boys swung their car onto the highway in pursuit of the thieves' automobile, it already was a good distance ahead, Frank at the wheel was barely able to keep their quarry in sight.

. "Maybe a speed cop will get those fellows," he said hopefully, as the automobile ahead shot past a red light, hitting sixty miles an hour.

But no motorcycle officer happened to be cruising about at the time. In a few minutes the thieves turned onto a side road which led into open country. Once out of the city limits, Frank stepped up his own speed and gradually began to overtake the other car.

The driver, apparently aware that he was being chased, swung off onto a dirt lane. Here the going became rough. The narrow road, which led into Barmet Woods, was full of curves and hollows. The Hardys lost sight of the other machine.

Suddenly, swinging around a sharp curve, they came upon a motionless object lying in the center of the road ahead. Frank jammed on the brakes to avoid hitting the still form, and the car skidded to a stop.

"It's a deer!" cried Joe.

He jumped from the automobile and ran over to the animal. Although its body was still warm, the deer was dead. It was only too clear what had happened.

"Those thieves must have struck it!" the boy cried furiously. "We'll have to report this to the game warden."

There was nothing the brothers could do for the animal, so they carried it to the side of the road and jumped back into their car to continue the chase. They had not driven ten yards before there was a report like a pistol shot from the left rear tire, and the machine swung violently.

"Blowout!" exclaimed Frank in dismay.

He stopped the motor and the two got out again. The tire was flat and useless.

"Well," shrugged Joe, "I guess the chase is over as far as we're concerned. Those men will be halfway through the next county by the time we get this tire changed."

The brothers worked as fast as they could, removing the ruined tire and putting on the spare. But so much time had elapsed that they could not hope to overtake the other automobile.

"No chance of catching those men now," said Joe. "I never saw more nervy thieves in all my life."

"Maybe we'll see them again and can turn them over to the police."

Turning over lawbreakers to the authorities was not a new experience for the Hardy boys.

From the time they had solved the mystery of the Tower Treasure, the brothers had brought many a criminal to justice.

Frank and Joe were the sons of Fenton Hardy who had earned an enviable reputation as a detective with the New York Police Department. He had been so successful that he had established himself in private practice, locating in the city of Bayport.

Although Fenton Hardy had never intended that his sons should follow his profession, preferring that they study medicine or law, the lads had taken matters into their own hands. In their early teens they had shown marked ability in deduction and had solved many baffling cases. Only recently a mystery concerning Melted Coins, involving a gang of coin thieves and a "Mr. Spanish," a foreign visitor who had lost his memory, had been brought to a successful conclusion by Frank and Joe.

So adept had the boys become in solving mysteries that by now it was pretty well agreed in the Hardy household that they had shown the talent and earned the right to carry on the Hardy tradition as detectives. One requisite of a good detective is perseverance, and the brothers determined at this moment that the auction thieves should not escape.

"But right now we 'd better get back to Chet,"• suggested Joe.

"First we'll call up the game warden and tell him about the deer," said Frank.

They stopped at the first telephone they came to and made the report. "When the brothers reached the Suydam mansion, they found that the auction was over. At first the boys thought the place was deserted. Then they spied Chet, sitting gloomily on the porch steps beside a large stuffed bear, a bear cub, several small animals, and an odd-looking collection of boards, knives and implements of no recognizable use.

"A fine pair!" grumbled the stout boy. "Where did you go? I've been sitting here waiting and waiting for you."

The Hardy boys told their chum about the thieves.

"So that's where the stuff went?" said Chet. "The auctioneer was awful upset over it. Said he was going to report it to the police. Well, how about getting this stuff down to your place?"

"To our place?" gulped Joe. "Aren't you going to take the animals home?"

"Mother won't stand for it. You don't mind if I take them to your house, do you?"

"Before we say 'yes,' suppose you answer a few questions," Frank suggested. He and Joe sat down on the steps. "What's behind all this mystery anyhow? Why did you drag us to this auction?"

"Yes, and what on earth do you want with a lot of stuffed animals?" demanded Joe. "And all this other junk?"

"It isn't junk," declared Chet hotly. "That's a taxidermy set. I got it at the auction. Real bargain, too."

"What are you going to do with it? You don't know anything about taxidermy."

"I know more than you think. I answered an ad in a magazine a few months ago, and I've been taking a-a correspondence course since then."

"So that's your secret?" asked Joe.

"Yes, but a fellow can't really follow the course unless he has equipment to work with. Now I have the equipment but my mother won't let me do any animal stuffing at home. So I guess it will have to go to your house."

The Hardy boys looked doubtful. They had an idea that Aunt Gertrude would have a good deal to say about such a scheme.

"Well, come along," said Frank. "Load the stuff in the car. Maybe we can set up your outfit in the attic-and maybe we can't. Too bad we couldn't have brought that deer along with us. You could have practiced on it."

"What deer?" asked Chet.

The brothers told him about their pursuit of the thieves' car and about the deer that had been struck and killed on the country road.

"The very thing!" squeaked the fat boy. "Just what I need. Lesson Eight in the correspondence course has full instructions for mounting deer. Let's drive out there and see if the game warden will let me have it."

When the boys reached the spot, the official was just putting the deer into a truck. Chet made his request. In the end the boys followed the game warden to his office, and the would-be taxidermist was given the head and pelt on which to try his skill.

An hour later the Hardy boys and Chet pulled into the driveway beside the Hardy home and began unloading their strange cargo.

"We'd better take this stuff in the back way and up the kitchen stairs to the attic," said Joe. "No use getting the house all dirty. I'll see if Aunt Gertrude is around."

He tiptoed up onto the back porch and peered into the kitchen. The quick-tempered lady was not in evidence. Joe came back and helped Chet carry the stuffed bear up the steps.

The animal was awkward to handle, but the stout boy hoisted the forelegs over his shoulders while Joe picked up the hind legs. Chet was bent over almost double with the weight of his burden. Grunting, he managed to get the back door open. He set the animal down on its rollers and pushed it into the kitchen. Instantly there was a wild shriek from within the room.

"Help! Help!" screamed Aunt Gertrude.

The boys' aunt wheeled in flight but missed the doorway to the hall. She ran full-tilt into the wall. Backing, she bumped into a chair, which promptly overturned. Another shriek followed as the rolling bear reached her. She bolted wildly in another direction, straight for a basket of freshly ironed clothes.

That was the climax. The woman lost her balance and went headlong into the basket, just as the bear came to a stop in front of the stove.

"Aunt Gertrude!" cried Joe, who had rushed into the kitchen, "I'm terribly sorry."

He helped his relative to her feet. Regaining her composure somewhat, the woman glared first at the inanimate bear, then at the boys.

"It's all my fault," said Chet sheepishly.

"So!" Aunt Gertrude snapped. "Chet Morton, eh? I might have known it."

That ended plans for transporting Chet's taxidermy equipment and animals to the Hardy attic. The bear was hastily lugged out of the kitchen while Aunt Gertrude with clipped sentences and a pointing finger issued orders for its removal. Chet's tools, the bear, the other stuffed animals and the head and pelt of the deer went to the loft over the garage.

It seemed best to the three boys that they stay out of the woman's sight as much as possible for a day or two, so they busied themselves with work in the new taxidermy shop. The task of washing the pelt of the deer was in full swing the next morning when Fenton Hardy climbed the stairs. He watched the proceedings for a while, remarking that he thought he would prefer to stick to detective work.

"How about helping your Dad?" he asked his sons. "I have to go out, and I'd like you to listen to the short-wave broadcasts for a while. A clue may come in on the Hudson case. If it does, phone the police at once."

"All right, Dad," returned Frank, glad of a chance to turn from taxidermy to mystery.

He and Joe already had discovered that Chet 's interest in taxidermy fell short of actual work. The fat boy sat on the side lines and read directions out of a large book, while Frank and Joe toiled at the job of washing the deerskin.

They left Chet with the task and went into the house to listen to the new set their father had purchased. For a while the powerful receiver brought in nothing but the usual grist of air lane signals, police news, and uninteresting ham conversations as Frank tuned in one frequency after another. Then, abruptly, an urgent call broke in on the Bayport police broadcast.

"Calling cars fifteen, eighteen, twenty. Calling cars fifteen, eighteen, twenty. Fifteen proceed at once to the Acme Electronics Company -- "

"Listen to this!" yelled Joe. "The Acme outfit is the largest electrical supply firm in Bayport."

"- investigate a robbery," continued the police announcer crisply. "Eighteen go south to State Highway. Twenty go north to State Highway. Locate and stop light green truck with stolen batteries, license number beginning Z41. Calling cars fifteen, eighteen, twenty -- "

"I'll phone Chief Collig and see if he thinks this might be a Hudson gang job," Joe said excitedly.

He ran off, while Frank remained at the radio.

CHAPTER III.

THE IMPOSTOR.

"Just picked up your call," Joe told Chief Collig, who was an old acquaintance of the boys. "What's that? You do think it's the Hudson gang? I see--"

Joe turned away from the telephone and went back to Frank, who was still tuning the radio from one short-wave frequency to another to pick up any possible messages from the gang itself.

"Get anything?" asked Joe.

"Nothing Dad would want."

At the moment the radio was blaring forth sounds like a parrot screeching.

"Better get that noise off or Aunt Gertrude will be in here!" grinned Joe, and then told what Collig had said.

Back on the police frequency the boys could hear further directions to the patrol cars. After a time it became evident that the light green truck had not been located. Cars fifteen, eighteen, and twenty were called in. Half an hour later Chief Collig telephoned the Hardy home to say that the stolen batteries had not been recovered.

"Acme says the loss runs into a lot of money," grumbled the Chief. "Besides, those batteries were very special. They can't be replaced at any price."

Fenton Hardy returned to the house a few minutes afterward. "Well, any news?" he asked.

"A gang of thieves just made a big haul from the Acme Electronics Company," Frank told his father seriously. " Chief Collig says it looks like the work of the Hudson gang."

Fenton Hardy snapped his fingers with irritation. "Eight under my very nose!" he muttered in disgust. "I had a telephone tip that Spike Hudson might be in town and that's why I went out. But I didn't expect a daylight robbery. Spike usually works at night."

"What does he look like?" asked Frank.

Mr. Hardy rummaged through his files. In a moment he handed a photograph to his sons. It was the picture of a surly, heavy-featured man with bushy eyebrows.

"That's Spike Hudson, leader of the Hudson gang," he said.

The brothers studied the face until certain they would recognize the suspect if they should ever see him. For some time the boys talked over the case with their father. In the end he decided to run out to the Acme factory to check up.

"I'm sure there won't be another robbery today," the detective said, as he reached for his hat, "so you boys needn't listen to the radio any longer."

After he had gone Frank suggested to Joe that they sell their ham outfit in the attic.

"Good idea,," agreed Joe. "The one Dad bought is so much finer. Wonder what we can get for ours?"

"Probably not much. But let's go up and look it over."

Aunt Gertrude had other plans for them, however. She had discovered a moth in the upstairs hall. Aunt Gertrude and moths were mortal enemies.

"They come from all those old clothes of yours in the attic," she declared. "I want you to take them out and hang them on the line in the back yard."

Secretly the hoys chafed under the task, and it was only because their good ski suits were mixed in with the other clothes that they took any interest at all in the work.

"Look at this," said Joe presently, spying a discarded toy. "Our electric train set."

"We sure used to have fun with that," smiled Frank. "Remember how fast it would go when we stepped it up? Maybe we ought to give the set to some poor kid."

"I 'm willing," agreed Joe. " We'll keep our eyes open for one."

As Frank was carrying out the last piece of clothing from the attic, he discovered their skis in a far corner. They were very fine ones, and the brothers prized them highly.

"Wouldn't do any harm to wax the skis," Joe said.

"Swell idea. It'll keep 'em in good shape for next winter."

The boys settled down on the back steps of the house and began waxing. They had been at work several minutes when Joe suddenly remembered Chet.

"Forgot all about our hard-working friend," he said and grinned. "I suppose he's still up in the loft washing that deerskin."

A shadow fell across the grass. The boys looked up and saw a tall, gaunt man who had sidled around the corner of the house so silently that he was within a few feet of them before they became aware of him.

"Deer, huh?" he growled. "That's just what I've come to see you two boys about. I owned that deer."

"What deer?"

"The one you fellows killed. My pet deer. You ran it down deliberately, and don't deny it, because I've got the evidence."

"You're wrong about that," said Frank. "We saw the dead deer on the road, but it wasn't our car that killed it."

The lean man glowered at them. "I've got evidence you fellows killed the animal. Deliberately, too. That deer was worth fifty dollars to me, but if you'll pay for it, I won't make any trouble. If you don't pay, I'll go to the police!"

"We're not paying anything," said Joe firmly.

"Make it twenty dollars, then," said the man. "I don't want to see you boys go to jail."

"We didn't kill the deer and we won't pay a cent," said Prank, who had become suspicious of the fellow.

The man was too insistent about money; and he had offered no proof that he was the actual owner of the deer. As for his "evidence" against them, the boys knew he had none, because they were innocent.

"Ten dollars," wheedled the stranger. "Surely it's worth ten dollars to you guys to keep out of trouble. Think of the disgrace to your family."

"We didn't kill the deer. So we pay yon nothing."

The man turned away, muttering. "You haven't heard the last of this," he snarled. "I gave you a chance to get out of this trouble. I'm not through with you!"

He ambled off up the driveway and down the street.

"Wait here," said Frank to his brother. "I'm going to do some phoning. If that fellow ever owned that deer or any other deer, I'm a monkey's uncle."

Five minutes later he returned to the steps,

"Just as I thought!" he exclaimed hotly. " I phoned the game warden and found out the deer belonged to the county."

Joe whistled. "So that skinny fellow found out about the dead deer and thought he'd raise a little money, eh?"

"For all we know, he may have been in the car that killed the animal."

Just then Chet Morton came down the driveway, swinging a package. He had been to town to buy some disinfectant for his work. When he saw the waxed skis, he assumed an expression of deep injury.

"A fine pair of helpers you are," he scoffed. "I give you a lesson in taxidermy and then you walk away and forget to come back. I thought you had to help your father."

"We were just wondering how you were getting along. Got that pelt washed yet?" asked Frank.

"That's going to be an expensive animal before I finish with it," said Chet ruefully. "I just met the man who owned it."

"Tall fellow? Looked as if he hadn't had a square meal in a month?"

Chet nodded. "Yes. I felt sorry for him, he looked so hungry. That deer was the only pet he had. He seemed to think we had killed the animal, so--"

"You didn't give him any money?" cried Joe.

"Only ten dollars," confessed Chet. " I think you fellows ought to chip in and pay part of it. After all, the poor man--"

"The poor man was a crook," declared Frank, getting up.

Quickly he told the stout boy what he had learned from the authorities. Chet's eyes popped open. He turned pink with surprise, then purple with indignation.

"Why, the low-down thief!" he yelled. "I'll get that fellow. So help me, I'll mow him down.

Ten dollars of my hard-earned money!" He appealed to his chums. "Come on, fellows, now's your chance to show what kind of detectives you are. Here's a real case. A confidence man has just gypped your best friend out of ten dollars. Can't you track him down for me?"

The brothers grinned at each other. Frank patted Chet on the back.

"Rely on us, pal," he said. "We'll take your case. Go on back to your taxidermy. We'll see what we can do."

The Hardys had no real expectation that they would be able to pick up the trail of the hungry-looking stranger, but at least it offered an escape from taxidermy. They went off downtown, thinking that perhaps some of their friends in the Bayport Police Department might be able to give them a lead toward locating the crook.

The possibility that they might run across the fellow by accident was slim, they realized. Nevertheless, when they were in the business section of Bayport and hardly a block from Police Headquarters, they suddenly caught sight of him in the crowd ahead.

"Look!" cried Joe, grabbing his brother's arm.

Frank already had spotted the tall man above the other pedestrians. As the two boys gave chase, some instinct seemed to warn the crook that he was being pursued. The Hardys were only a few yards away from him, when suddenly

he dashed from the crowd and bolted down a narrow alley.

Frank and Joe scrambled in pursuit. They were just in time to see the stranger run full-tilt into a gang of ragged youngsters who had dashed from the rear of a store. He was delayed only a moment; then he sped on.

One of the urchins stumbled headlong against Frank. Joe leaped aside to avoid trampling him. By the tune the three were sorted out, the tall man had vanished. The lads, except for the youngster who had collided with the Hardy boys, had vanished too-into a convenient dark doorway.

"Lemme go!" squeaked the boy, whom Frank was helping to his feet. "Here comes a cop!"

The lad writhed out of his grasp and ran like a jack rabbit, ducking into the cellarway where his companions had disappeared. Plunging toward the Hardys from the far end of the alley came one of Chief Collig's men-Policeman Con Biley.

"Did you see a gang of boys down this alley?" puffed the officer, as he reached the brothers. He was a trifle shortsighted, arid at first he did not recognize Frank and Joe. "Oh, it's the Hardys!" he exclaimed. "What are you doing here?"

"We were after a fellow who gypped Chet Morton out of ten dollars," said Frank quickly. "Tall, thin man. He ran in here. Did you see him?"

"Nobody like that came out the other end of the alley," declared Riley firmly. "But he sounds like a small-time crook by the name of Elly Batter."

"Then he must have gone into one of these stores!" cried Frank. "Come on, Joe!"

CHAPTER IV.

BOYS OF THE ALLEYS.

FRANK and Joe separated. For ten minutes they hunted up and down the alley, looking into the rear entrances of all the stores. Elly Batter -if he was their man-had made a good getaway.

Policeman Eiley, still puffing, was busy on his own account. But he was having no better luck than the brothers.

"Where did those kids disappear? That's what I want to know," he said in disgust.

"What were they doing?" asked Joe.

"A lot of petty thieving's been going on," grumbled Eiley. "I was after three of the young pests. Old Mr. Smith on Main Street thinks they took candy from his store. You didn't see 'em?"

"Yes, we saw them," Frank replied, but said no more.

It seemed a shame to him to arrest the boys who perhaps were innocent. On the other hand Mr. Smith might be right. While Frank was trying to decide what to do, Riley moved on up the alley in his search. After he had gone, the Hardy boy lifted the cover of the cellarway where the lads had disappeared and looked in, expecting to find the youngsters still crouching there. But they had vanished.

"The hares got away from the hounds this time," grinned Joe.

He and Frank went on through the alley to the street from which Con Eiley had come. There was a small, rather dark ice cream parlor around the corner. Inside, looking in the showcase of candy, was the urchin who had collided with them. Beside him were two of his chums.

"Let's go in and talk to them," suggested Frank. "Maybe we can find out if they're guilty."

The ragged youngsters looked up warily as they recognized the boys.

"You didn't squeal on us, did you?" whispered the one nearest the door.

Joe grinned and shook his head. "Why should we? How about a soda?"

"Sure thing!" the urchins said eagerly.

The Hardy boys sat down at the counter and ordered sodas for everyone. The little fellows, at first suspicious, gradually thawed out. Frank and Joe could see that there was nothing vicious about them; but clearly, they were neglected.

"Pa and Ma are away from home all day," said Jimmy Gordon, obviously the leader of the trio. "They don't know if I go to school or not." He looked at his companions. "We all flunked this year, 'cause we stayed out a lot. We're supposed to go to summer school three days a week," he grinned.

"How about your meals?" asked Joe.

The three lads laughed scornfully. "We get our own-when we get 'em!"

"Well, then," said Frank, "if you have to cook your own supper tonight, how about eating with us?"

"What's the catch I" asked one of the boys suspiciously.

"No catch at all. Come along home with us and let's eat. You'll have a swell dinner. My aunt's a wonderful cook."

The three lads had a brief conference among themselves; then Jimmy Gordon spoke up.

"O.K.," he said. "We'll take a chance. But if this is a gag to turn us over to the cops, it's gonna be just too bad for you."

When Frank and Joe arrived at the Hardy household shortly before six o'clock that evening with three of the dirtiest and raggedest urchins who ever had set foot on High Street, their Aunt Gertrude glared at her nephews. When she learned that the lads had been invited to dinner, she threatened to pack her suitcase.

"What!" she exclaimed, as Frank argued with her in the kitchen out of earshot of the youngsters. "Have those filthy little imps sitting in our dining room! I should say not! Your mother would never forgive me."

"Aunty," said Frank solemnly, "those boys are hungry. Of course they're dirty. They're neglected. But when I told them about your cooking - about the sort of meal they'd have - why, Aunty, you should have seen their faces!"

Aunt Gertrude softened. "Well, of course, if they're really hungry, that's different," she said. "Take them upstairs to the bathroom and get them cleaned up. But don't use the good guest towels," she warned.

By the time dinner was served, the three boys had been scrubbed and shampooed until they glowed with cleanliness. Aunt Gertrude vowed she hardly recognized them, and insisted they could not be the same lads.

Fenton Hardy, coming in just as dinner was being served, was astonished to find the young guests present, but he took in the situation at a glance. When Aunt Gertrude saw how the trio, once their first shyness wore off, attacked the steaming plates of food, she beamed with pride. Miss Hardy always declared afterward that the highest compliment ever paid her cooking was the eating performance she witnessed that evening.

"I declare," she would sigh reminiscently, "one would think those young wolves hadn't been fed from the day they were born."

Chet, who had gone home to dinner, drove over just as the group was finishing the meal. He blinked a little when he saw the three young strangers seated at the table.

"How about my ten dollars?" he asked the Hardy boys, ignoring their frantic signals to be quiet. "Did you catch the crook?"

"What crook was that? " asked Fenton Hardy before his sons could reply to Chet's question.

"I gave the boys a case," Chet explained. "After all, they're detectives, aren't they? I hired them to go after a crook -- "

"Detectives!" yelled Jimmy Gordon, scrambling out of his chair. " I knew it, fellows. This is all a gag to turn us over to the cops. Scram, guys-scram!"

The three youngsters made a rush for the door. Aunt Gertrude, with great presence of mind, collared young Jimmy. Chet grabbed another, while Fenton Hardy captured the third lad as he was heading for a window. It took a good deal of talking to convince the lads that they were in no danger from the police and that they were among friends. Chet, to make amends for the fright he had caused them, offered to give the youngsters lessons in taxidermy.

"It's a fascinating hobby," said the fat boy enthusiastically. "I'll let you mount some of the smaller animals on boards, if you have real talent. Come up tomorrow and I'll show you how it's done."

"They have to go to school," said Frank.

"We don't go much," spoke up Jimmy Gordon. "We could come in the morning."

"No school, no taxidermy," said Chet firmly. "How about it?"

The three boys looked at one another.

"O.K.," sighed Jimmy. "We'll be here after three tomorrow."

Frank and Joe took the boys home, prepared to explain to the lads' parents why they had kept them out so late. But the ramshackle flats where the boys lived were in darkness.

"My Pa's just as likely not to come home at all. I don't see much of him," said one of the boys.

The Hardys got a promise out of each of them that they would be in bed in ten minutes. Jimmy Gordon was reluctant to leave his benefactors, however.

"You're good guys," he said. "And you have a swell Pa. But I've got a smart uncle. Elly Batter's his name."

"What does he look like?" asked Frank quickly, trying not to betray his interest in the name of Elly Batter.

"High as a church and thin as a pencil," grinned the youngster. "He's smart, Uncle Elly is."

"Where does he live!"

"I dunno. He used to stay with us, but Pa put him out. So long. See you tomorrow." Jimmy scrambled up the dimly lighted stairs of a shabby tenement.

Frank and Joe were thoughtful as they walked home. For a moment they had hoped for a clue to the fellow who had Chet's ten dollars. But they would have to locate him some other way.

"Jimmy's background is pretty bad," said Frank. "Poor kid! What chance has he got?"

"That's up to us," declared his brother. "We'll see that he gets a chance. We can't let him follow in his uncle's footsteps!"

"You're right."

Promptly at three-thirty the next afternoon, the three youngsters trudged into the Hardy yard and knocked on the back door. They carried their schoolbooks with them as proof that they had kept their end of the bargain.

"Where are those animals we're going to mount?" demanded Jimmy Gordon as Frank opened the door. "Lead us to 'em."

The Hardy boys escorted the lads to the workshop. Chet beamed with pleasure. To tell the truth, he was getting a little bored with taxidermy already. Besides, Frank and Joe had scarcely shown up in the workshop all day because they had been listening to short-wave conversations.

Chet had been obliged to do all the work himself. He figured if he could have three assistants, willing and eager to learn, he might be able to give his entire attention to the serious study of taxidermy. In the meantime, the assistants would do the actual work.

"Now, boys," said the fat youth, leading the youngsters toward the work bench, "I'll explain just how this is done. You will notice that I have a deer--"

"It's all hollow. Has no insides," objected Mickey Walsh, a redhead who was the youngest of the trio.

"Quite true," said Chet. No one noticed that young Jimmy Gordon had lingered to examine some bottles of chemical at the end of the loft. "Now, to stuff this deer--"

Suddenly there was a crash and a piercing scream. The boys wheeled. Jimmy Gordon lay writhing on the floor, his hands over his face. Beside him was a shattered bottle of acid.

"My eyes!" he shrieked.

CHAPTER V.

THE STUFFED WOLF.

FRANK picked up the screaming boy and carried him to the house. Aunt Gertrude came rushing downstairs, took one look at Jimmy, and hurried back to her room for her sulfa salve. Joe ran to the telephone to call Doctor Franklin.

When the physician arrived, he pronounced young Jimmy's injuries fortunately not so severe as had been feared. The acid he had upset had burned him slightly, but his sight was not endangered. Doctor Franklin said that Aunt Gertrude's prompt first-aid treatment had been a great help, and that the lad would be all right.

"He won't even have a scar," the man stated.

"He's a lucky boy, and no thanks to this taxidermy work," scolded Aunt Gertrude, glaring at Chet Morton. " I want every bottle put under lock and key."

That ended the taxidermy lesson for the day. Chet went home. Although he was thankful that Jimmy had not been injured, he was sure the accident would frighten his new assistants away. With Frank and Joe busy solving a mystery, he would have to do all the work himself?

The next morning his fears were confirmed. There was no one to help him. Fenton Hardy had asked his sons to copy some figures for him and listen to short-wave broadcasts while he was out of the house. The boys had two radios going, a fact which had sent Aunt Gertrude into the country for a few hours.

"I'm getting a little fed up with this arm-chair mystery solving," Joe said to his brother as he finished copying the figures for his father. "I'd prefer action!"

"So would I," agreed Frank, as he tuned in various frequencies on the new instrument. " But if we 're going to work for Dad, we'll have to do everything his way."

The boys listened patiently to the radio for two hours, picking up many bits from police reports, foreign broadcasts, and ham conversations, but they heard nothing they thought could have come from the Hudson gang.

Then suddenly there came a wild medley of noises that sounded more like a cat-and-dog fight than anything human. Frank was about to switch to another frequency when an idea came to him.

"That noise is on the same frequency as the parrot screeching we heard," he announced. "Wonder if it means anything."

"Some ham trying to be funny," Joe commented, not impressed. " The authorities ought to trace the fellow and make him stop."

The boy said he was tired of listening to the radios, and if Frank did not mind he would run out to the garage loft to see how Chet was getting along with his taxidermy work.

"After all," he remarked, "we've certainly left our fat friend in the lurch for a long time."

"You'11 be sorry if you go out there," laughed Frank, "because he'll put you to work and decide to loaf himself."

"I'11 take a chance."

As Joe went out the back door, he met Chet walking across the yard.

"Come on down to Roundtree's store with me," the stout boy said. "I want to buy some glass eyes."

"Glass eyes! What for?"

"Did you ever see a stuffed animal without eyes?" inquired Chet reasonably.

"All right, all right," said Joe. " I knew you weren't going to buy them for yourself."

Mr. Roundtree was a real taxidermist. His cluttered store, on a downtown side street, was as dark as a cave and twice as mysterious. From the shadows of its dim interior, white fangs and sharp teeth gleamed menacingly at the boys. Near the door, a huge grizzly bear reared on its hind legs as if ready to pounce on any customer who earned his master's displeasure. Mr. Roundtree himself was a short, fat man who shuffled around in carpet slippers.

He was talking to a customer when the boys entered. Apparently the man and the store owner were dickering about the price of a stuffed wolf, which stood on the counter. In the gloom of the store Joe could not see the person clearly, for he wore a hat low on his forehead, but it seemed to him that there was a familiar ring to the man's voice.

"All right, then, I'll take it," said the customer as Chet and Joe examined an extraordinary collection of glass eyes in a display case. He paid for the stuffed wolf and picked it up from the counter.

"Don't you want me to crate it?" asked Roundtree.

"Too big. I'll carry it as it is," the other muttered.

Joe tried to get a good look at the fellow as he went by, but he carried the stuffed wolf in such a way that his face was hidden completely. He brushed past the boys and hurried from the store. Joe had a distinct impression that the man had tried to avoid being seen. He also felt that he had met him before in some unpleasant encounter. Could he be the hard-looking fellow who had outbid Chet the day of the auction?

"Do you know that man's name?" Joe asked the taxidermist.

Roundtree shook his head. "Never saw him before. Paid cash for the wolf, so his name was none of my business. What can I do for you fellows?"

"I want to look at some glass eyes," said Chet. "Have you any that will do for a stuffed deer?"

As the taxidermist opened his showcase, Joe hurried to the street. He looked up and down, but though the man with the wolf had left the store not fifteen seconds before, he was nowhere to be seen.

"Queer!" reflected Joe. "Must have jumped into a car."

A glance at the solid bank of parked automobiles by the curb, however, told him that this was impossible. There was no gap in the line of cars as there would have been if one had pulled out within the past few moments.

The Hardy boy decided that the mysterious customer must have gone into some near-by store. But after glancing into a grocery, a bakery, a market, a florist's shop and a new store dealing in electrical equipment, Joe had to reject this theory. He spoke to a girl standing in front of the florist's window.

"Did you see a man go past carrying a stuffed wolf?"

The girl looked at Joe suspiciously. "What's the joke?" she asked.

"No joke. I mean it. A man came out of Roundtree's a minute ago. He was carrying a stuffed wolf. I'm trying to find out which way he went."

The girl shook her head. "I didn't see him, and I've been standing here for the past five minutes, waiting for a friend."

Joe was deeply puzzled. He walked back up the street just as Chet emerged from the taxidermist's shop.

"That's a mighty strange thing," said Joe. "The fellow who was in Roundtree's place - he's disappeared, wolf and all."

"How could a man disappear with a stuffed wolf? Everyone who saw him would remember him."

"Apparently no one saw this fellow. Chet, I have a notion he's the person who outbid you at the auction and cheated the auctioneer."

"And was in the car that killed the deer?'" asked Chet. "Say, we'd better find him," the stout boy added, as the full import of the matter dawned on him. "Gee whiz, maybe I can get back my ten dollars!"

They went down the street in a hurry. The(c) traffic cop on the corner had seen nothing of a man carrying a stuffed animal. A postman advised the boys to stop playing jokes and go home.

"Strange!" said Chet to Joe as they went back toward Roundtree's.

As the chums passed Zetter's new electric store again, they heard a scream of alarm. It was a woman's voice.

Joe and Chet dashed into the shop. There were no customers in the store, nor was there anyone behind the counter. Joe spied a passageway leading to an alley back of the shop just as the scream was repeated.

"This way!" he shouted, and dashed to the rear, followed by his companion.

A woman stumbled into the passageway through a back door. Pale with fright, and gasping, she pointed outside.

"I've been bitten!" she cried. "By a wild animal!"

The woman's screams already had attracted a crowd. The traffic cop and the postman raced into the store, as did a scattering of curious bystanders

Joe and Chet ran into the alley back of the building. It was deserted. There was no animal in sight and no human being either. Behind them, the boys could hear the woman shrilly insisting that a wild animal had attacked her just outside the door. The traffic cop and the postman came into the alley, took a look around, and went back into the store again.

"She's crazy," Joe heard the postman saying. "Imagining things."

"Maybe she's not so crazy as they think," remarked Joe. He noticed an outside cellar entrance under Zetter's electric shop. "Come on, Chet."

The boys went down the steps. There, just inside the doorway, its teeth gleaming balefully in the shadows, stood the stuffed wolf.

"I guess that's the wild animal, all right," said Chet. "But what happened to the owner?"

At this moment a man came clattering down the cellar steps. He was Mr. Zetter.

"What's going on here?" he demanded. "I step out of my store for a minute, and when I come back, everything's in an uproar. What are you boys doing? And what - Great Scott!" he exclaimed, backing away. "What's that?"

"It's a wolf," returned Joe. "Don't worry. It isn't alive."

"Well, get it out of my cellar," shouted Zetter. "I don't want it!"

The boys carried the wolf up to the alley and stood it against the rear of the building. The store owner insisted that they take it away.

When Chet and Joe declared that they did not own the animal, he told them not to bother. So the wolf was left standing against the wall.

"Well, we may as well go back," said Chet.

When the boys reached the Hardy home a few minutes later and told Frank the story, he was puzzled and interested.

"Now why would a man pay good money for a stuffed wolf and then dump it into a cellarway five minutes later, unless he wanted to hide it! I'd like to have a look at the thing," he said.

Frank and Joe went downtown together and made their way along the alley to the place where the wolf had been left. The stuffed animal was no longer there. As the Hardys stood wondering about this, Mr. Zetter came out the back door of his shop.

"Well," he said, "I 'm glad you took that confounded wolf out of here. I certainly didn't want it around my store."

"But we didn't take it!" declared Joe.

"Then who did?" asked the man blankly.

"I wonder," mused Joe, as Mr. Zetter went inside to wait on a customer.

"What's the matter, fellows?" piped up a young voice behind them.

The boys turned to see a blue-eyed, freckle-faced lad smiling up at them.

"Jimmy Gordon!"

The ragged little fellow repeated his question.

"Jimmy," said Frank, "did you see a stuffed wolf near this doorway any time in the past fifteen minutes?"

The youngster nodded. "Sure did," he replied. "At first I thought it was real."

"Do you know what happened to it?" asked Joe.

"A fellow came in a truck and took it away."

Frank and Joe looked at each other. The same thought crossed both their minds; they probably had missed their chance to nab the auction thief.

CHAPTER VI.

SIGHT ON WILLOW RIVER

""Would you know the truck if you should see it again?" Frank asked young Jimmy Gordon,

"I think so."

"Keep your eyes open then, and if you do see it, get the license number and let us know right away. Or, if you see the man who took the stuffed wolf, try to find out who he is. Will you do that?"

"You bet!" declared Jimmy, his eyes shining. He was thrilled at being allowed to help. It was a great deal more fun to be on the right side of the law than on the wrong, he decided. "I'll tell the gang," he added, and raced off down the alley.

When the Hardy boys returned home they told their father about the incident, remarking that the mysterious stranger who had avoided Joe in Roundtree 's shop no doubt was the man who had cheated the auctioneer.

"He was afraid I'd get the police after him," said Joe.

Mr. Hardy nodded. "No doubt he himself was hidden in that cellar," said the detective. "You should have looked for him there."

Joe was crestfallen, though he was glad to be taught a lesson by his experienced father, The crook must have waited until the boys had gone away, then taken his wolf off in a truck he had parked in the alley.

"Don't give up the chase too soon, or your man will get away from you," advised Mr. Hardy. "Now for another job. Do you boys think you could install transmitting and receiving sets in your car and on the motorboat?"

"Yes, Dad," Frank replied. "It's a good thing we didn't sell the one in the attic. We thought of doing so."

"Is something up I" asked Joe eagerly.

"I've decided to be ready for all emergencies," returned Fenton Hardy. "You'll find a short-wave set in the back of my car. That'll do for the roadster. The one in the attic-try to put that in your boat."

The boys went upstairs to effect the transfer. Frank switched on the transmitter to be sure it was working properly. Joe turned on the receiver. Suddenly, as he switched from one frequency to another, he heard a call that sent shivers down his spine.

"Help-Hudson!" a voice said faintly.

There was something uncanny about the weird appeal for help.

"Frank," said Joe excitedly, "it's on the same frequency as those cat and dog and parrot noises. Do you suppose there's any connection?"

"Looks like it. We'd better tell Dad about this right away," Frank decided, and led the way downstairs.

"Your father's in his study entertaining an old friend," Aunt Gertrude warned them. " Better not go barging in there unless it's important."

"This is important, all right," her nephews assured her, and tapped on the door.

"Come in!" said their father.

"We heard the call again," whispered Frank excitedly, after he had beckoned to Mr. Hardy to come to the hall a moment. "The same call we heard just before the Acme robbery. 'Help -Hudson.' We just picked it up."

"Maybe it means something else is stirring," added Joe.

Fenton Hardy looked grave. "You may be right," he said. "I'll put in a phone call to the police right away. In the meantime," he added, "I want you boys to meet an old friend of mine." He took his sons into the study.

A lean, white-haired man with a kindly, cultured face was sitting near a window. He shook hands with the boys.

"You've heard me speak of Professor Wood," said Mr. Hardy.

"Of course," replied Frank. "You're the famous explorer."

"Well-not so famous," answered the elderly man modestly. "I have traveled around the world a bit. Go ahead and attend to anything you have to, Fenton, while I get acquainted with these sons of yours."

After the detective went out, the boys chatted with the scientist. He told them he had just arrived in the United States after an exploratory journey to the Gobi Desert in Mongolia.

"Actually," he said, "I'm a naturalist, rather than an explorer. There were several others in my party but I left ahead of them. I have been expecting the rest to arrive by plane, but they're overdue."

He was telling the boys some of his experiences in the desert when Mr. Hardy came back. Excusing himself, the detective spoke to his sons.

"I've notified the State Police to be on the lookout for trouble," he said. "They're covering every large electrical supply warehouse and retail store. In the meantime, how about you boys standing by on the short-wave set upstairs and reporting anything else suspicious?"

The boys hurried to the attic. For the next half-hour they sat listening, but did not hear the call of "Help-Hudson" again, nor anything else that might bear on the case. Finally they heard the telephone downstairs ring. A few minutes later Fenton Hardy called up to them.

"All quiet on the Bayport front," he reported cheerfully. "And in all the surrounding territory, too. The police say there have been no robberies nor attempted break-ins. Everything looks clear. But they're going to watch those places again tonight in any case."

"I hope they don't think we gave them a false alarm," said Joe.

"On the contrary, they think that a robbery might have been planned but the thieves were frightened off."

The boys decided to start at once installing the short-wave sets in their roadster and the motorboat. It did not take long to put the new two-way outfit in the car; but to get the old one down to the boathouse on Barmet Bay and make it fit into the Sleuth and work clearly was another matter. It took longer than they expected, but at last the task was finished.

"Sounds good," grinned Joe, as he gave the radio a final test. " Gives the old Sleuth class!"

"Hope we catch the Hudson gang with it," said Frank, as they started home.

As they neared the house, Aunt Gertrude called to her nephews from the porch.

"It's Chet Morton," she said. "He's on the phone. Wants you to come to a party."

Frank went in to take the call.

"Look," said Chet, "I can't spend all my time stuffing animals and you two can't spend all your time tracking down criminals. "We need relaxation. We need fun. We need music. My sister and I are having a few of the crowd over, so why don't you and Joe take a spin out to the farm?"

"Sounds swell," declared Frank. "Eight away?"

"Any time you can make it. But wait a minute. Biff Hooper won't be able to come unless somebody picks him up. You know he has a summer job at Cooper's factory on Willow River and doesn't get off until nine o'clock. He's a guard, and he's on duty from five in the afternoon until the regular night watchman comes on."

"Maybe we could pick him up in our boat," suggested Frank. "Instead of going to your place by car, we'll take the Sleuth and go up the river. After we pick up Biff, we'll walk over to your place."

"That," said the wily Chet, "is just what I hoped you'd say. See you about nine-thirty then."

Shortly before nine o'clock the trim fast motorboat, the Sleuth, which the Hardy boys had bought with reward money for solving one of their most exciting mysteries, moved out into Barmet Bay. While Frank steered the speedy little craft, Joe tuned in the receiver of the newly-installed short-wave set. There was nothing exciting on the air, however.

The Sleuth headed toward the mouth of Willow River, which emptied into Barmet Bay. It was a pretty stream that meandered through the farming country adjacent to the city. The factory where Biff worked was about a mile from the bay.

It was dark when the Sleuth reached the factory area. The boys peered through the gloom, looking for a light in the building.

"Strange," shouted Frank, above the hum of the engine. " I can see the outline of the factory but I can't see any-what's that?';

Out of the night came the distant wail of a siren. The weird sound rang through the darkness for a moment. Then, just as it was rising in volume, it was cut short.

The boys listened, but the siren did not sound again.

"I think there's something wrong at the factory!" snapped Joe.

Frank nodded in agreement and opened the throttle. The hum of the engine rose to a roar as the Sleuth plunged forward.

As it neared the factory landing, Frank cut the motor. He swung alongside the pier and the Hardys sprang out. Quickly they snubbed the boat to the pier and ran across the dock in the darkness.

Halfway up the path to the factory Frank tripped and went sprawling. Joe, close at his heels, leaped over the object that had caused his brother to stumble.

"Joe, it's a body!" gasped Frank. "Your flashlight, quick!"

Joe switched it on, and the boys gasped. Lying on the path was Biff Hooper. Their chum was sprawled on his back, unconscious.

"Look after him, Joe," Frank ordered, after a hasty examination showed them that Biff was alive. "I'll go phone for a doctor. And the police."

As he ran up the path, he whipped his own flashlight from his pocket. Its clear white beam showed him the door of the factory office. It stood open.

Frank hurried inside and felt for an electric switch beside the door. Finding one, he moved it, but there was no answering glare of light. His flash, however, showed him a telephone on a near-by desk. It also revealed the office to be in a state of confusion. A chair had been overturned. The floor was littered with papers. And the door of the office safe hung open.

Frank grabbed the telephone. But when he listened for the usual hum, there was only a dead, empty silence that indicated a broken line.

"Wires cut!" he muttered.

Just then he heard the roar of a truck's engine start up. Flashlight in hand, he hurdled the upturned chair, sped from the office and down the side of the building. He was just in time to see a dim hulk moving off down a back road. The truck's passengers, whoever they were, must have seen the gleam of light through the windows and lost no time in clearing out.

The Hardy boy ran around to the front of the office. Two figures were lurching up the path.

"I've got Biff," said Joe from the darkness. "He's all right-knocked out for a while, but I brought him around. Help me get him into the office. Did you call the police I"

"Phone wires are cut," said Frank briefly. "I'll use the radio transmitter in the boat."

Biff was groaning and rubbing his head. 4 * Some watchman I am," he muttered. " Bunch of fellows slugged me when I was making my rounds. Boy, does my head hurt-I"

Joe set Mm down in one of the office chairs, while Frank hurried down the path to the dock. It was a good thing they had installed the shortwave set in the boat, he thought.

"Dad's always right," the boy concluded. "I'll follow his advice any day."

He leaped into the Sleuth and crouched down by the radio, tuning the set to the Bayport police band. It was a few moments before he got a response. Then he heard the familiar voice of Sergeant McLeod, acknowledging his code number.

"Come in-come in," said the police officer brusquely.

"Frank Hardy calling. Reporting assault and robbery. Watchman slugged. I'm at the--"

Before he could give the location of the trouble, something struck him a smashing blow on the head. The boy pitched forward over the radio set, unconscious.

CHAPTER VII.

AUNT GERTRUDE LISTENS IN.

A DARK figure crept up the path to the factory.

"That settles one of 'em!" the man gloated, advancing cautiously toward the office. He could see a glare of white light inside-the beam of Joe's flashlight. As he reached the door, a twig snapped under his foot. In an instant the flashlight was turned full on him.

"Why, it's Tim!" cried Biff Hooper, recognizing the husky fellow who stood in the doorway. "It's all right, Joe. This is the night watchman. He was to relieve me at nine o 'clock."

Quickly he told Tim what had happened.

"I thought there was some dirty work on foot here," the watchman grunted. "I nabbed one of 'em anyhow. Turn on a light and let's see what happened here."

"The lights are out and the phone wires are cut," Joe told him.

"Give me that flash a minute," the watchman said quickly, reaching for it. "I'll fix the lights!"

He disappeared down a corridor. Shortly afterward the office lights went on.

"Just as I thought," said Tim, returning. "They tampered with the box. The telephone wires won't be fixed so easy." He looked around the ransacked office and whistled. " Robbery, huh?" He peered into the open safe. "Got away with all them special quartz crystals." Tim straightened up. "It'll go hard with that guy down in the boat. He was just gettin' fixed to clear out when I nailed him."

Joe jumped up. "What's that?" he cried. "Where's Frank?"

It had occurred to him that there might be some connection between Tim's encounter with one of the supposed bandits and the fact that Frank had gone down there to use the radio.

"Was there more than one boat at the dock?" he inquired quickly.

"Just the one," declared Tim. "Probably the boat them thieves come in. I tapped this fellow over the head and left him there. He'll keep."

Joe, fearful, ran from the office. He raced down the path. At the dock he stopped short.

The Sleuth was gone!

In the meantime, Frank's interrupted call for help had not gone unheard. Sergeant McLeod, at Bayport Police Headquarters, had relayed it at once to Chief Collig, who immediately picked up the telephone and called Fenton Hardy.

"Queer thing just happened," he told the detective. "We picked up a short-wave call from your son Frank. He started to report some trouble when we lost contact. Do you know where he might have been?"

"He and Joe went up the Willow River in their motorboat to pick up a friend at Cooper's Quartz factory. I'll phone the place and ask the watchman if he saw them," said Fenton Hardy quickly. "I'll call you right back."

When the detective tried the number of the factory, the operator reported that the line was dead. He became alarmed and rang Headquarters.

"Pick me up here in your car, Chief," he suggested. " The factory telephone wires are dead. Looks as if something's wrong out there."

"I'll be outside your house in three minutes," said Collig briskly.

Aunt Gertrude had overheard her brother talking on the telephone. Sensing trouble, she came downstairs in her dressing gown.

"What's wrong?" she demanded anxiously. "Have the boys gotten into difficulty again!"

"I'm afraid so," said Fenton Hardy.

He hurried outside before Aunt Gertrude could cross-examine him. After he had gone, the good lady paced the floor nervously. She felt helpless and a little frightened to be in the house alone. If a hounded criminal should come in, it would not be the first time. Gertrude Hardy had learned long ago that living in a famous detective's home was precarious business.

"What's that?" she thought suddenly.

Something was wrong. There were strange noises in the house. She prowled about, trying to find the source of the disturbance, her heart beating wildly.

She ran the noise to earth at last. It came from the new radio to which Fenton Hardy had been listening in his study before he had mad(c) his hasty departure.

' 'Do-re-mi-do-re-mi-f a-so-la-ti-do."

Somewhere, someone was trying to sing the scale. Aunt Gertrude's first reaction was that the man's voice was bad-very bad indeed. Her second reaction was that he should not practice over the radio.

She decided she did not want to hear any more of it, but when she attempted to turn it off, she could not do so. Aunt Gertrude's knowledge of the radio set was limited. Though she twisted and turned various gadgets, somehow she could not manage to get rid of the gentleman singing the scale.

"Drat that man!" she muttered impatiently.

She was still trying to find out how to do away with him, when she suddenly realized that the monotonous reiteration of the scale had changed. The man was inserting words-and very strange words at that, about every third time he sang the scale.

"Don't-delay-so-land-the-do-"

Miss Hardy knew of no voice teacher who would think of giving a pupil such a selection to sing.

"Fenton and the boys would say that's a signal of some sort," Aunt Gertrude told herself. Snatching up pencil and paper from the writing desk, she settled down on the couch to listen.

The voice went on singing the scale, but did not repeat the words. The woman had just began to think her ears had deceived her, when she suddenly heard the phrase again. Quickly she wrote it down.

"Fenton will be interested in this," she thought excitedly, waiting for more strange words to be sung.

Aunt Gertrude no longer was eager to turn off the radio. Instead, the good woman sat perfectly rigid on the couch, pencil poised in her hand.

Meanwhile, Chief Collig, two policemen, and Fenton Hardy had been racing along the Willow River road in the officer's car. The detective's face was tense with anxiety. The fact that Frank had called the police to report trouble was serious enough; that the call had been cut off gave rise to a dozen surmises.

"I certainly hope nothing has happened to those boys of yours, Mr. Hardy," said the Chief, as the car swerved around a curve with a screech of tires. "They're smart lads. But I've always figured they weren't quite old enough to be tackling the sort of work that really belongs to the police."

This was a delicate allusion to the fact that on more than one occasion the Hardy boys had solved cases that Chief Collig felt might have been worked out, in due time, by his own staff. While the Hardy boys and the Bayport police cooperated with one another in the cause of justice, there was some resentment against "the two kids" on the part of veteran members of the detective staff.

The police car swung into the short road that led from the highway to the factory. When it pulled up in front of the office, Fenton Hardy was relieved to see Joe hurrying up from the river.

"Thank goodness, you're safe, my boy!" he exclaimed.

"But how did you know about this, Dad?" gasped his son in astonishment. "The phone wires were cut."

"Frank flashed us by short-wave," explained the Chief. "Where is he? And what's been going on here?"

"Frank has disappeared."

"Disappeared!" cried Mr. Hardy.

Hastily Joe told his father and Chief Collig what had happened. Biff Hooper, new feeling much better, and Tim, the night watchman, emerged from the office and added what details they could.

"Quartz crystals?" said Collig, when he heard they had been stolen. "And the thieves got away with the stuff in a truck!"

"Chief, I'd like to get back to io^n at once," said Fenton Hardy, his voice low and husky.

"Shouldn't we stay here and look for Frank I" objected Joe.

"Your brother was in a boat," said his father, "We won't find him by hunting in a car. What we need is a boat."

"I'll get you a police boat," stated Collig. "Come on!"

He shouted instructions to his two men to stay at the factory and keep a sharp lookout. He, Mr. Hardy, Joe and Biff jumped into the automobile. The officer swung the car around and headed for Bayport.

Speaking rapidly into his short-wave transmitter, Chief Collig gave curt directions to the sergeant on duty at Headquarters, ordering him to send a police boat out at once.

"Tell the men to meet me at Calhoun's Wharf," he directed. "And get word to the State Police to check all highways for that truck."

As he turned off the transmitter, Collig grinned at Fenton Hardy. "Modern police methods are pretty good, eh?" he chuckled.

"You're doing your best to help us rescue Frank," Mr. Hardy admitted.

Ho looked grim and worried.

CHAPTEE VIII.

THE MAN IN THE BUS.

THE short-wave communication system of the Bayport Police Department proved its effectiveness. The police boat was waiting below the wharf slip when the Chief's car reached the mouth of Willow River. Fenton Hardy and Joe transferred hastily to the launch.

They thought Biff would want to go home, of course, but the lanky youth insisted he felt much better and wished to join in the hunt for Frank, He climbed in beside the others.

Chief Collig said he would go back to Headquarters and direct the search for the thieves from there. He gave orders to the sergeant in charge of the launch to keep the boat out all night if necessary-in short, to continue the search until Frank should be found.

The powerful engine purred rhythmically as the launch sped upstream. Its brilliant searchlight swept the dark waters and shone on the leaves of the trees by the river's edge. They saw nothing.

"The Sleuth may have drifted away," said Biff hopefully.

"Afraid not," replied Joe. "It was tied too tightly for that to happen."

Fenton Hardy and the boys gazed out over the river as the launch moved along. Although the big searchlight swung steadily from bank to bank, probing into its dark recesses, they saw nothing suspicious on the entire run to the dock at Cooper's factory. And there was no sign of the missing Sleuth.

"Now what, Mr. Hardy?" the sergeant asked.

"Go up the river as far as you can," the detective replied.

The search was continued as far as the Falls, then the pilot turned back.

"We'll try the bay," Mr. Hardy decided, deeply worried.

Half an hour later, with the searchlight scanning the black waters of Barmet Bay, and the searchers still finding no sign of Frank and the Sleuth, the group began to admit defeat. The Hardys became very concerned. The sergeant, more to make conversation than for any other reason, asked:

"You're sure you didn't hear the engines of the motorboat at any time, Joe!"

"Not a sound."

"How it could have drifted so far in that short while--"

"Look!" cried the boy suddenly.

Far out in the bay he had seen a flash of light. It was followed by another and then another. Three long flashes-then three short ones again,

"SOS! Someone signaling for help!" exclaimed Joe. " Let's go!"

Fenton Hardy got out his automatic. "The Hudson gang could be pulling a fast one," he explained. "Boys, get down in the bottom of the boat!"

The launch ripped through the water. In a few minutes, directed by the flashing gleams in the distance, it approached a shadowy object tossing in the waters. The policeman switched on his searchlight, which shone full on a familiar boat.

The Sleuth!

It was drifting sluggishly. Crouched in the bow, flashlight in hand, was Frank Hardy. He was alone.

"Thank goodness, my boy is safe!" muttered Fenton Hardy tensely.

Joe tossed a rope to his brother and tied the Sleuth fast to the police launch. Then the smaller boat was pulled alongside and Frank scrambled on board.

"Don't ask me how it happened," he said. "I couldn't tell you. All I know is that when I woke up I was drifting out here in the bay, with a bump on my head, a galloping headache, and no gas."

"No gas!" exclaimed Joe. "The tank was full when we left the boathouse."

As the sergeant swung the launch around and headed for Bayport, Frank was told all the details of the mystery since the time Tim, the watchman, had knocked him out.

"I hope he never hits one of you," said the Hardy boy with a wry grin.

When the Sleuth was back in her boathouse,, Chief Collig was informed by telephone that the search had ended. No one-least of all Frank -knew exactly what had happened, and one guess seemed to be as good as another.

"The main thing is that Frank is safe," said Fenton Hardy.

"And the Sleuth, too," added Joe dryly. "I'd hate to lose it."

"As for me," went on the detective, "I'm going home. You boys had better come along."

"But we started out to go to a party at Chet's place," Joe pointed out. "Everyone will be there. "What do you say, Biff?"

"Sure thing. Chet and the others will want to hear about our adventure."

"They can hear about it from you and Joe, then," said Frank. " I 'm going home with Dad. My head still hurts from that wallop."

No amount of coaxing could induce the boy to change his mind, so Biff and Joe set out for the Morton farm by bus, hoping that the party would still be in full swing by the time they arrived.

"I'll be glad to crawl into bed," said Frank as he and his father ascended the steps of their home a short time later. "I wish I knew who ran the Sleuth around and then let it loose."

"I'm inclined to believe it was one or more of the thieves," decided Mr. Hardy.

"I thought Joe said they went off in a truck."

"No doubt some of them did," replied the detective. "But you and Joe may have made them change their plans in a hurry. Fate played into their hands, and one or two men may have carted the stolen quartz crystals off in your boat."

"They must have gone a good distance to have used so much gas," remarked Joe. " And why would they set the Sleuth adrift? To cover their tracks?"

"Exactly. It would take a cunning, evil mind to think out that one-a mind like Spike Hudson's."

Fenton Hardy's jaw set as he finished speaking. Frank knew this boded ill for the crook whenever the detective should lay his hands on him.

When the two Hardys stepped into the hall, they were surprised to hear the radio going. It was tuned to a short-wave frequency. They were equally surprised not to find Aunt Gertrude rushing forward to ask about her nephews.

"It's strange," remarked Fenton Hardy, as he walked into his study. "Most unusual for Gertrude to--"

He uttered a gasp of astonishment. His sister lay stretched out on a couch near the radio. On the floor beside her was a scrap of paper with writing on it.

"Do-re-mi-don't-delay-so-land-the-do-" read Frank.

"Gertrude!" shouted Fenton Hardy, rushing to the side of the unconscious woman and shaking her. "What's the matter? Gertrude!"

The woman came to with a start and uttered a cry of fright. When her brother and nephew learned that she merely had been sleeping, they were vastly relieved.

"The idea!" she stormed. "Waking me up like this. Can't a body lie down for a nap without having her head shaken off?" Then she spied Frank. "My gracious, boy, I'm so glad you're back home safe and sound. Where on earth were you? And what do you mean by frightening us all the way you did?"

"I certainly didn't plan to frighten anyone, Aunty," confessed Frank.

He told her briefly what had happened during the evening, whereupon his relative shuddered and hugged him and cried a little and scolded him all over again for upsetting her.

"You gave us a scare yourself," remarked her brother. "For a moment I was afraid there 'd been foul play here."

Frank showed his aunt the scrap of paper which he had picked up from the floor. "Did you write this?" he asked. "It says: 'Do-re-mi-don't-delay-so-land-the-do.' "

"I heard it on the radio tonight," his relative replied. "I'm sure it's an important signal," she added proudly.

Frank Hardy and his father studied the paper thoughtfully.

"It may be," the latter said slowly, after he confirmed the fact that the strange singing had been heard on the same frequency as the cat-and-dog fight and the parrot screeching.

"But what does it mean?" asked Aunt Gertrude.

"So land the do," mused Frank. '"Oh!" he exclaimed. ' 'Do is probably d-o-u-g*-h. Money!"

"Of course," said Miss Hardy. "Fenton, you'd better trace the broadcaster of those words at once. I told you it was a signal-I knew from the start--"

The detective already was on his way to the telephone. While he was gone, Frank kept repeating the strange message: "Don't delay so land the dough." Had Spike Hudson or one of his men spoken it?

Mr. Hardy returned and relayed a conversation with Chief Collig. "I asked him to check on all cars and trucks that might have shortwave equipment," he said. "The Chief told me he'd received word of another robbery tonight. Radio tubes, this time. It was in a town about fifty miles from here. He'd been asked by the Harpertown police to stop all trucks passing through Bayport. Not a thing has been found yet."

"That do-re-mi message had something to do with it," declared Aunt Gertrude firmly.

"You may be right," admitted her brother. "Or it may have been intended as a signal to the thieves at the factory where Frank and Joe were."

Aunt Gertrude suddenly called to their attention how late it was and retired. Frank, weary from the evening's excitement, went to his own room. But Fenton Hardy sat down at the new radio to listen for any possible clues to the doings of the Hudson gang.

Joe, meanwhile, was enjoying himself at Chet Morton's party. He and Biff created a sensation by their story of the evening's events on the riverfront. The stout boy pretended to be crestfallen because he had missed the excitement.

"Nothing like that ever happens to me," Chet complained. "I could prowl up and down Willow River for a week, but would I be slugged on the head and kidnapped? No, sir. The worst that would happen to me would be a cold in the head."

"I guess you're right," teased his sister Iola, who incidentally was looked upon by Joe Hardy as the most interesting girl in town.

The party broke up shortly after refreshments had been served. Normally, Joe would have escorted Callie Shaw home. She was the pretty and vivacious girl who was Frank's special partner at Bayport High School functions, but this night she had decided to stay with Iola Morton. So Joe went home alone, catching a bus at the nearest highway stop.

As the vehicle roared toward the center of the city on its final run of the night, the Hardy boy noticed that he had one fellow-passenger-a man who was dozing in a rear seat with his hat brim pulled down over his eyes. Joe, puzzling over the strange events that had taken place on the river earlier in the evening, paid scant attention to the man. When the bus finally reached High Street, however, and Joe got off, he glanced up just as the solitary fellow raised his hat brim and peered out the window. The youth had a startling shock.

The man was the one who had taken Chet's money; the one Policeman Riley had said might le Elly Batter!

Already the bus had pulled away from the curb. Joe ran after it.

"Stop!" he shouted. " Stop!"

But the driver did not hear him. The big vehicle turned a corner and roared off down Main Street.

CHAPTER IX.

THE NEW WALLET

IT was seven o'clock the following morning. The two Hardy boys stood on a street corner in a shabby section of the city, looking up at a rambling, unpainted tenement, because Joe had picked up the trail of the thief of Chet's money; or at least he thought he had.

"You might have been mistaken, yon know," said Frank.

"I think not," insisted his brother. "I saw the man's shadow against the window shade in that second floor room last night. I'm sure it was the thief's."

"Why did you say you thought so? I've forgotten. Guess I was half asleep when you told me."

"I saw the bus driver at the terminal and he said the man got off at Bridge Street. When I walked along here, I saw a tall, thin man against the window shade in that room."

Just then a slatternly woman came out of the tenement. Frank stepped up to her and smiled.

"Pardon me," he said politely, "but could you tell us the name of the man who lives in that room on the second floor?" He indicated the window Joe had pointed out.

The woman looked at the boy suspiciously.

"What d'you want to know for? Are you bill collectors?"

"We're trying to locate a man we know. My brother thought he saw him come in here last night."

The woman shook her head. "Andrew Smith didn't come into that room. He went out. The fellow who rents that room works nights. He usually gets dressed to go out about two o'clock in the morning."

"Thank you," said Frank.

The Hardy boys turned away, disappointed.

"That will teach me not to jump to conclusions," said Joe.

The boys walked back up the street. They had hardly reached the corner before they heard someone calling their names. Turning around, they saw young Jimmy Gordon legging in pursuit.

"Gee whiz, I'm glad I saw you fellows," panted the lad. "I was just going to your house. I got a problem."

"Problem, Jimmy?"

The youngster nodded. "You know Mickey -the redheaded kid who was with us the other day. Well, he's in trouble. Awful trouble."

"What happened?"

"He got caught. The cops nabbed him stealing buns from the bakery down the street. He's at the police station now, and I'm scared they're going to send him away. It ain't the first time he's been in trouble. And he wouldn't have got in this fix, only he got hungry, see."

The Hardy boys glanced at each other.

"All right, Jimmy," said Frank quietly. "Let's go down to the police station and see what we can do."

At headquarters they had a brief conference with Chief Collig, who took them into the judge's chambers. Judge Robertson, of the Juvenile Court, was to hear Mickey's case within the hour. He listened carefully while the Hardys, whom he knew well, told him what little they knew of Mickey and his background.

"He isn't really bad," Frank assured the judge.

"Very few of these lads are," the judge agreed.

"He's a neglected boy," Frank went on. " No one takes any interest in him. He's half starved, too."

The judge looked intently at the earnest youth before him. "Now if Mickey had a big brother-someone responsible and willing to look after him--"

"How would two big brothers do, sir?" asked Joe eagerly. "Frank and I'll take him in hand."

"I hoped you'd say that," smiled the judge. "Very well, then. If you'll take an interest in Mickey, I'll turn him over to you on suspended sentence. But remember-he's no angel. You'll have your troubles."

When the judge learned that the Hardy boys would give the lad work in the taxidermy shop over their garage, and pay him for his efforts, he was loud in his praise. He called Mickey in and told him of the arrangement.

"How about a job whittling perches for stuffed birds?" Frank asked the youngster.

"Gee, I'd sure like that," declared Mickey enthusiastically. "Can I start now?"

"Sure thing," said Joe. "But first comes breakfast at our house."

As was to be expected, Aunt Gertrude looked askance at the freckle-faced urchin, but gave him second helpings of everything she had cooked. When Chet arrived for work in the taxidermy shop a little later, Mickey was turned over to him, since this was one of the days he did not have to go to summer school. The lad settled down to his job of whittling.

"Call this work?" he grinned. "It's fun!"

Frank and Joe had a conference with their father, who told them he had heard the "Help- Hudson" call on short-wave the evening before. Thinking it might be a signal for another robbery of electronic equipment, the detective had warned the police to be on the lookout.

"But nothing happened," said Mr. Hardy. "I'm beginning to wonder if some employee inside the factory who has access to a short-wave transmitter notified the thieves to stay away when he learned the police were near-by. I believe I'll go do a little interviewing," he concluded suddenly. "Suppose you boys take on what I planned for the morning."

"Glad to, Dad," they said. " What is it? "

"Investigate the grounds around that crystal quartz factory."

Within ten minutes the brothers were ready to leave. As they were going out the door, Professor Wood came in. The boys delayed a moment to ask him if he had heard from his scientific friends who were overdue in their flight back to the States from Mongolia.

"Unfortunately, no," the elderly man replied. " The government has tried to make contact, but so far there hasn't been any report." The boys noted a catch in his voice as he spoke.

Mr. Hardy greeted his caller and the brothers went on their way. They got out the car and drove along the Willow River road toward the factory grounds. At the site of the robbery they began to explore the earth carefully.

"I'll take this side," said Frank. "Suppose you inspect the other. Then we'll meet here and go down to the dock together."

Frank found nothing but a slip of paper. It was blank. Joe saw footprints but they proved to be those of Biff Hooper. Presently the brothers joined forces again and walked to the water's edge. At the dock there was not a clue.

"The thieves covered their tracks well," remarked Frank.

"Sure did. Here's something, though."

Joe had spied a set of muddy footprints on another path which ran down the river bank. As he took measurements of the marks Frank kept on looking. Suddenly he spied something lying among the weeds. He stooped to pick it up.

"Nice new wallet!" lie exclaimed, flipping it open.

The leather case contained no money, no papers, no identification cards. It was as new and as empty as if it had just come over the store counter.

"Might have fingerprints on it," Frank suggested. "Let's take the wallet home and give it the test."

The boys drove back to Bayport. They were not too hopeful that the empty case would prove valuable to them, but they had long since learned that the most innocent and unpromising clues often were the most vital in solving a mystery and that none should be overlooked.

After putting the car in the garage, they decided to go upstairs for a moment to the taxidermy shop. Chet and young Mickey were working. That is to say, Mickey was working and Chet was giving him instructions.

"Jimmy's here, too," said the fat boy. "I just sent him into the house for some food."

The brothers smiled. That was just like Chet; always thinking of something to eat.

"How do you like the new job, Mickey!" asked Joe.

"Swell," returned the youngster. "I bet I'll be the best perch-whittler in Bayport."

"And that's covering a lot of territory, sonny," said Chet with a fatherly air. "At any rate, you haven't cut off a thumb yet. Just follow my instructions and you'll be all right."

The fat boy drew the Hardys aside and showed them a snapshot which Jimmy had brought.

"It's Elly Batter," he whispered. "And he's the fellow who gypped me out of my ten dollars!"

The brothers stared at the picture. Chet was right.

"You've practically got your money back," said Joe. "It'll be easy now to get hold of this thief."

The boys said no more, because Mickey was walking over to ask Chet something. The Hardys went downstairs and crossed the yard. Joe opened the screen door to the kitchen. As he did so, they heard a shriek of terror. Aunt Gertrude bolted through the kitchen and shot past him out the doorway!

CHAPTER X.

A LONG WAIT.

"Aunt Gertrude!" exclaimed Frank. "What's wrong?"

"A skunk!" the woman gasped. "Bight in the front hallway. Of all things! A skunk!"

The boys investigated, but with due caution. There was a small black and white striped animal in the hall, truly enough, but it was quite motionless and completely harmless. The skunk was a stuffed one.

Joe heard a noise of strangled laughter. On tracing it to its source, he dragged young Jimmy Gordon from behind the living room curtains.

"So! Frightening Aunt Gertrude, were you?"

"I didn't mean to-honest," insisted Jimmy. A grin flickered over his face as he recalled the woman's wild leap of horror when she had spied the supposedly offensive animal. "Chet sent me into the house for some food. I had the skunk with me and I set it down for a few minutes. I was just coming back when I heard your aunt on the stairs."

"You'd better slip out the front door and get back to the taxidermy shop before she sees you," advised Joe. "Otherwise Aunt Gertrude will never give you another meal!"

The boy vanished and Frank told his aunt there was nothing about which to be alarmed. Miss Hardy's relief when she learned that the skunk was long past being able to throw off a scent was very great, but she was indignant that the stuffed animal had been left in the hall.

"Looks like one of Chet Morton's tricks," she fumed. " I'll give him a piece of my mind!"

The ringing of the telephone put an end to further questioning which might have led to discovery of Jimmy Gordon's part in the affair. The call was from Fenton Hardy, who wanted to speak to Frank.

"I've been doing a little interviewing," said the detective to his son. "It's about the Hudson gang and these queer radio messages."

"Anything we can do to help?" asked Frank.

"Later, yes. I want you and Joe to meet me at Mawling tonight. Six o'clock at the Bed Lion Restaurant. We'll have dinner there. I may have a job for you by then."

Frank conveyed the message to his brother. Then they went to the cellar to make the fingerprint test on the wallet. Unfortunately, it was so covered with marks from various persons' fingers, they could distinguish nothing.

"Well, that clue got us nowhere," remarked Joe. " By the way, I want to make some adjustments on the radio in our car."

"I'11 help you."

Young Jimmy came downstairs from the taxidermy shop to watch the procedure. The boy anted to know why it was called" short-wave" when it could go so far.

"It's hard to explain," said Frank, "but think of a piano with high and low notes."

"You mean the way the notes vibrate?" asked Jimmy.

"That's right. The shorter the radio wave, the more it vibrates or cycles each second, and the further it leaves the earth's surface before it bounces back. So the frequency of the vibrations determines the signal's range, or distance from the transmitter."

"Sounds interesting," grinned Jimmy. "Say, that looks like a good set you got in the car. Not so good as the one my Uncle Elly owns, though. He has a swell short-wave radio -the kind you talk over."

The Hardy boys were interested. So Elly Batter owned a transmitter!

"Would you like me to get you a portable like his?" continued Jimmy. "I can get it cheap."

"Where?" asked Joe quickly.

The boy hesitated. "My uncle can get one for you," he said at last. "He makes them at Ms factory."

"At his factory? Then let's go there and see your uncle now," said Frank eagerly.

Jimmy again hesitated. He scratched his head reflectively.

"Well, I'm not sure about where the factory is," he said. "I heard my Uncle Elly talk about it but I never went there myself."

"How could we see him?"

"I know where he lives now. Ma told me. Want to go there?"

"Eight away," said Frank with a wink at Joe. He climbed into the car. " Get in, Jimmy. Show us the way."

The Hardys glanced at each other significantly, feeling sure they were on the trail of something which might prove even more important than getting back Chet's ten dollars. Neither believed for a moment that the slicker, Elly Batter, owned a radio factory. Undoubtedly this was a lie he had concocted for the benefit of his relatives, to explain his possession of an expensive short-wave set with a transmitter.

How had he got the outfit? Was he mixed up in an illegal radio market? Or connected with thieves of electronic equipment? Elly Batter would certainly bear investigating from more than one angle.

Jimmy acted as guide, directing Frank up one street and down another until at last the car reached a section of the city that seemed strangely familiar to the brothers.

"Here we are," said Jimmy at last. "Uncle Elly has a room in that house right across the street with a man named Smith."

Frank brought the car to a stop. The house pointed out by the lad was the same one to which Joe had trailed the man on the bus!

"I'll go and see if he's in," said Jimmy, hopping from the automobile.

The Hardys followed the lad across the street and up a flight of stairs in the tenement. On the second floor Jimmy halted at a door on which was a card marked Andrew Smith. He knocked.

A woman poked her head out of an apartment down the hall. "Who do you want?" she asked roughly.

"I came to see my uncle," said Jimmy. " He lives here."

"Not any more, he don't," returned the woman. "He moved out yesterday."

The lad stared at her. "That's funny. He didn't tell my Pop and Mom he was going away."

"He made up his mind sudden. Anyhow, there's no use knockin' 'cause the place is empty. So you'd better clear out."

Jimmy was sadly perplexed as he went down the stairs with Joe. Frank hung behind to ask the woman if more than one person had not lived in the now vacant apartment.

"No," she said. " Andrew Smith and nobody else." She was quite positive on the subject.

So Elly Batter was using an assumed name! And lying about the fact to his own sister. But no, maybe it. was only Jimmy who had been told the lie. Perhaps Mr. and Mrs. Gordon also were involved in something dishonest!

Beaching the car, Frank told Jimmy he would like to call on the boy's mother. "Will she be at home f " he asked.

"I dunno. We can see."

Jimmy's home was a three-room flat, untidy and dirty. Mrs. Gordon was a discontented-looking woman with artificially blonde hair, but she was well-dressed and well-groomed.

"I brought visitors, Ma," announced her young son.

Mrs., Gordon seemed none too pleased to meet the Hardy boys. "I'm just getting ready to go out to work," she said. "I work part-time in a beauty parlor," she explained. " A woman has to have a little spending money for clothes and entertainment."

"It must keep you busy, looking after things here and working too," said Frank.

"Mr. Gordon and Jimmy have to look after themselves," she said languidly. Glancing at the lad, she added, "I'm going to the movies when I finish work, so you'll have to make your own supper."

"Ma, did you know Uncle Elly went away?" the lad asked her. "We went to see him just now, but he's moved."

"That so?" Mrs. Gordon seemed only mildly interested. "Must have got a job somewhere else."

Frank tried to find out more about the family's relations with Elly Batter. But he learned little. Though he felt Mrs. Gordon was holding something back, he became convinced that she herself was not dishonest.

As the boys were about to leave, they heard a commotion in the hall. Someone banged at the oor. When Jimmy opened it, two men came in, carrying a third.

"It's Pop!" cried Jimmy. "He's hurt!"

"George!" shrieked Mrs. Gordon.

Her husband, middle-aged, dressed in rough work shirt and overalls, was white-faced with pain. He nodded to them and muttered, "Just an accident," as the other men carried him across the room and set him down on a couch.

"He got brushed by a car," explained one of the men.

"Oh, George! Are you badly hurt?" cried Mrs. Gordon. "I can't stand it!" She sat down limply in a chair, covering her face with her hands.

Mr. Gordon sank back on the couch, gritting his teeth. "I'm O.K., "he said. "It could have been worse. Sprained my left ankle. Got my nerves on edge."

"Anything else we can do for you, George?" asked one of his companions.

Gordon shook his head. "I'll be all right now. 'Thanks for bringing me home, fellows."

"We'll look in tonight and see how you're getting along. Better get your wife to soak that ankle and tape it up. Lucky it wasn't broken."

"Oh, I wouldn't touch it!" cried the woman. "Jimmy, go call a doctor!"

The men went out. Gordon looked warily at the Hardys.

"Who are these two boys and what do they want?" he asked his wife crossly.

"We were looking for Uncle Elly," explained Jimmy. "He's gone away. They wanted to buy a radio."

Mr. Gordon's eyes narrowed warily.

"I don't know anything about Elly Batter or his radios and I don't want to know. I don't know where he went or where he is now, but if I did, I wouldn't tell you," he grunted. " Madge, get some hot water and bathe this ankle. I don't want a doctor!"

"I have to go," the woman said, "I'm due at work in a little while. Jimmy will have to look after you."

"Sure thing," spoke up Jimmy cheerfully. "We won't need a doctor."

Frank and Joe offered to help, but Mr. Gordon turned down their assistance and made it plain he wanted them to leave.

"Don't you worry. I'll fix him up," Jimmy said confidently.

"Poor kid!" Joe burst out as the brothers reached the street. "What chance has he got with that sort of home life?"

"We'll just have to see that he gets a chance," declared Frank. "By the way, I doubt that Mr. and Mrs. Gordon know very much about Elly Batter's activities."

"I don't trust that man entirely," Joe disagreed.

"Say, we'd better be on our way to Mawling. Dad'11 be waiting for us," his brother reminded him.

Mawling was a village not far from Bayport.

The town clock was just striking six when the boys pulled up in front of the Bed Lion restaurant. Fenton Hardy was not there.

The boys waited in front of the place for half an hour. Then they went inside and ordered dinner. Each time the front door would open, they would look up, expecting to see their father. But long after they had finished dinner, he still had not arrived.

The brothers went outside, walked up and down the main street, and finally returned to the restaurant. Their father had not appeared. By this time it was nine o 'clock. The proprietor of the establishment came over to them, a bunch of keys in his hand.

"Sorry, lads," he said, "but it's closing time. I lock up at nine."

The boys returned to the street. The owner extinguished the lights and locked the door. He walked off down the street.

"I can't understand it," Frank said. "Dad distinctly said six o'clock. If he knew he'd be delayed, I'm sure he would have phoned us. It's not like him to keep us waiting for--"

Just then they heard the shrill jangle of a telephone inside the locked restaurant. It rang again and again insistently.

"I have a feeling that call is for us," said Joe. "It's Dad, trying to reach us."

Frank turned and dashed toward a near-by store where there was a booth. "Maybe I can have the call switched here!" he cried.

CHAPTER XI.

THE SNEAKING FIGURE.

FRANK put a coin in the telephone slot and spoke quickly. " There's a phone ringing in the Red Lion Restaurant. The place is locked," he told the operator. "I think the call is for me. Could you have it switched here?"

"No phone ringing in the restaurant now," the girl told him.

"It was a moment ago. Could you trace the call and get the party? It's very important."

"Sorry. Too late to find out now."

Frank came from the store, discouraged. " I 'm sure it was Dad," he said to Joe. " What do you think we should do?"

"Go back home. If Dad tried to telephone the restaurant and received no answer, he may decide we aren't at Mawling. For that matter, he may be at home himself. We'd better go there."

"I think I'll phone the house," Frank decided. 4'Dad may have left a message for us."

Aunt Gertrude, upon hearing her nephew's voice, exploded at once. "No, your father's not here. Nobody's here, and me with a burglar on my hands--"

"What!" shouted Frank.

"Don't scream at me!" cried Aunt Gertrude. "I can't stand it. I've had enough trouble."

"Aunty, please. What happened?"

"Somebody stole one of Chet's animals."

"From the taxidermy shop?"

"Yes. I guess so. Anyway, I saw somebody come from the garage. It seemed funny for Chet to be working at night, so I called to find out who it was. But the fellow didn't answer. He started to run instead, so I knew he wasn't Chet."

"nd he had an animal with him!" Frank asked.

"Looked like it. But stop talking. You're wasting time. Get home here and do something about it!"

Frank repeated the conversation to his brother as they hurried toward Bayport.

"Gee, this business of stealing stuffed animals is getting close," said Joe. "Do you suppose Chet's was taken by the same fellow who gypped the auctioneer at the Suydam sale?"

"I wonder," mused Frank. "And why?"

As the boys became silent, Joe leaned over and switched on the radio to the frequency which had become synonymous with the Hudson mystery. Suddenly there was the sharp yelp of a dog. Frank swung the wheel, scanning the road ahead for the animal. Joe laughed.

"No danger of hitting that, dog," he said^ pointing to the radio.

Another bark emanated from the loudspeaker. But this time it was a different sort of sound.

Where the first had been the short yap of a terrier, this one was the full-throated bark of a larger dog. Then came a long-drawn-out howl, followed by the baying of a hound.

"First the parrot screeching, then the cat-and-dog fight. Now it's dogs," said Joe.

"I believe I'll notify the police," said Frank. "If there's anything to these sounds-if they're signals-maybe we can prevent another robbery."

Joe switched off the receiver and tuned in the transmitter to the local State Police Headquarters. But before he could use it, Frank cried out:

"Look!"

"What is it?"

The boys had reached the outskirts of Mawling. Against the skyline they could see the rectangular outline of a large building set back about fifty yards from the road. The place was almost completely in darkness.

"That's Turner's new battery factory, isn't it? "Frank asked.

"Yes. Did you see something suspicious?"

"Thought I saw a sneaking figure."

Already Frank had stopped the car. Now he was backing it up speedily. In a moment its headlights brought the building into relief.

"There he is!"

The car lights had revealed the figure of a man, crouched over, running across the grass in front of the factory. Instantly he swerved and rushed out of range of the light into the near-by; lackness. Frank applied the brakes and switched off the motor. He flung open the door on his side while Joe took the other. The Hardys leaped out.

"We'd better be quiet!" cautioned Frank.

Ahead of them in the darkness someone was running away swiftly. As the boys rushed in pursuit, they could hear the snapping of twigs as the stranger hurried to safety. Then silence.

"Where'd he go?" asked Frank, perplexed.

"I think over this way," said Joe.

He had snatched up a flashlight when scrambling from the car. Now he snapped it on.

"Be careful! Hold it way out to the side so he can't spot you!"

The boys moved cautiously toward the woods, playing the beam of light on the trees and bushes.

"Don't see a thing," said Joe tensely.

There was not a glimpse to be had of the mysterious figure they had seen from the car.

"We'll stand here quietly for a while and listen," whispered Frank. "He can't have gone far. He may give himself away."

Joe switched off the light, and they waited, motionless. Behind them the great hulk of the battery factory loomed mysterious and silent. There was not a sound from it; in fact, there was not a sound anywhere except the trilling of crickets and the croak of frogs in a distant marsh.

"Guess our man got away," concluded Frank a few minutes later.

Suddenly Joe wheeled and grabbed his brother's arm. "The car!" he cried out. "Somebody's trying to steal our car!"

He had heard the snap of the latch and the creak of hinges as one of the doors had been opened cautiously. Instantly the boys started to run. Joe again snapped on his flashlight. It picked out a shadowy figure seated behind the steering wheel of their roadster.

Frank yelled. To his surprise the figure in the car made no attempt to start the engine nor to make a getaway. He simply sat there. When the brothers rushed up, the flashlight shone clearly on the smiling face of Fenton Hardy!

"Dad!" gasped Frank. "You here! We thought--"

"I was a thief," finished the detective, laughing.

"Gosh, you sure gave us a scare," said Joe. "We thought someone was trying to steal our car. Then we would have been in a mess."

"Where did you come from, Dad!" Frank asked his father excitedly. "We waited and waited for you at Mawling, then decided to go home. Aunt Gertrude said-" Frank decided to save that story-"We saw someone moving toward the battery factory," he told his father, "so we stopped to investigate."

"Do you think he was a thief?" asked Joe.

"Well, hardly. You saw me," his father smiled. "I'm afraid I played a little trick on you when I realized who you were."

"It was you I soing up to the factory?"

"Yes. At first I didn't know my own sons were after me. Then when I realized it, I circled around to your car and found it unlocked." He shook a warning finger at them. "You see what could have happened if I'd been a real thief. You would have lost your man and lost your car, too."

The Hardy boys looked rueful. They realized only too well that their father spoke the truth, It would be a good object lesson to them.

"We won't do that again," said Frank. "And now, Dad, tell us why you're here."

"I've been checking up on this battery factory," said Fenton Hardy quietly. "I suspect the watchman. He seems to be a little too friendly with certain people who may or may not be radio equipment thieves."

"Is that why you wanted us to meet you in Mawling!" asked Frank. "You did say we'd get together at the Red Lion Restaurant, didn't you?"

"Yes, but I got tied up on an investigation in another village, and I just reached here a few minutes ago."

"Did you phone us at the restaurant?"

Mr. Hardy nodded. "When no one answered, I assumed the place had closed, and I was sorry to have missed you." He smiled at his sons. "Even if you made one error in judgment-I mean leaving the car unlocked-you proved yourselves good detectives, nevertheless, by spotting me on my way to the factory."

The boys were pleased to learn their father id not consider them a total loss to him in Ms work.

"Ah!" said Mr. Hardy suddenly, looking toward the factory. "It's time to get busy."

A gleam of light shone from one of the windows in the building.

"The watchman is making his rounds now," announced the detective. " We'll park your car near mine and do a little investigating."

He backed the automobile down the road a few hundred yards toward a woods. In the deep shadows Mr. Hardy brought it to a stop, locked the car carefully, and handed the keys to Frank.

"Come on!" he whispered. " Easy now, and no noise. We may run into a little excitement."

Cautiously father and sons stole forward toward the factory.

CHAPTEE XII.

JOE IN DISGUISE.

THE Hardy boys and their father circled around and approached the factory from the rear, where a dim light shone from a window on the ground floor. As they drew closer, they could hear music.

"I guess the watchman is sitting in the office listening to a radio program," whispered Frank.

The music was cut off abruptly. In its stead came the loud, angry snarl of a cat. Another cat chimed in. The night was filled with weird wails and yowls. Then they all ended as suddenly as they had begun.

"Do you suppose-" began Joe.

Inside the office an alarm bell clanged vigorously. Instantly the office light went out, but the din of the alarm continued. Fenton Hardy swung his boys around and urged them to run as fast as they could toward the woods.

"Must have stepped on a burglar alarm!" he panted as they sped off. " That bell meant us."

"Look!" cried Frank, glancing back over his shoulder. "Someone's signaling!"

A light shone just outside the office door. It was a sharp beam of a flashlight, which flickered on and off. The Hardys could read the code easily. Two longs and a short-Cr. Two short flashes-0.

From the shelter of the woods the Hardys watched. The flashes were repeated several times, but the signal never varied. Always the same word-go.

"I hear a truck," said Joe. " Maybe it's coming here."

"We'll find out," determined his father, and led the way toward the main road.

The flashlight signals were visible from the driveway leading into the factory grounds, although they could not be seen from the main road. Suddenly a car swung into the driveway. Its headlights were shut off a moment later and the brakes applied before it had gone more than a few yards. The automobile backed out swiftly, swung onto the highway again, and sped off.

"I'll follow him!" snapped Fenton Hardy. "The fellow meant to stop here but he caught the warning signal. Stay here and watch any other cars that stop."

He dashed off down a path among the trees. A moment later the boys heard the slam of a car door as their father sprang into his own automobile. The engine roared, and the tires bit into the gravel as the detective took up the chase.

His sons continued to watch the road. A few minutes later an oncoming truck slowed up and turned into the driveway. Again the warning flash from the factory. Like the other driver, this one hurriedly backed out to the main road and sped off.

"Shall we follow him in our car?" asked Joe eagerly.

"Dad said to wait. Maybe we're missing a good chance, but I guess we'd better stay here." Frank fidgeted under the restraint, nevertheless. " Oh, look!" he cried suddenly.

The truck, instead of continuing down the highway, swung to the left.

"The driver's turning up a side road! I'm going to cut across and see what's up," exclaimed Joe. "You hold the fort here."

"I may be in the roadster," called Frank, who suddenly had an idea perhaps he ought to be listening to a certain frequency on the shortwave radio.

Joe raced across the open ground in front of the factory, scrambled over a fence, picked his way through a small woods, and finally edged forward cautiously beside some bushes that bordered the side road.

There stood the truck, its lights out, its motor off. Joe crept closer. He could vaguely distinguish a shadowy figure in the cab.

Suddenly he heard a voice; a man's voice, gruff and peremptory. "Not tonight. I'll let you know," were the words.

That was all. No one answered. The engine of the truck roared into life, but the big vehicle, instead of moving forward, backed up the side road toward the highway.

Joe ran from his hiding place, hoping to distinguish the owner's name on the side of the vehicle. But the darkness was too intense. The driver reached the highway, switched on his lights, and tore off. Joe had a fleeting glimpse of the license plate, but he was too far away to read the number. One thing he did learn, however; it was an out-of-state license.

Crestfallen, the boy made his way back to his brother. He found Frank sitting in their roadster, listening to the short-wave receiver.

"No luck," reported Joe. "I heard somebody in the truck say, 'Not tonight. I'll let you know.' Then it backed off down--"

"Somebody in the truck said that?" cried Frank in astonishment. "I heard those exact words on this radio not five minutes ago. 'Not tonight. I'll let you know.' "

Joe's eyes widened. "Well, gee, maybe it was over a short-wave receiver in the truck that I heard those words!"

"Or someone in the truck was sending a message. "

Joe thought it over. "No, I believe it came over a radio. It was close enough to fool me, though. At any rate, when the truck driver heard it, he didn't lose any time clearing out."

"Perhaps it was a warning message from the factory watchman," suggested Frank.

The boys' speculations were interrupted by the return of Fenton Hardy. He parked his car near by and came over to them.

"Lost my man at the river," the detective reported, disappointed. "He just made the drawbridge with seconds to spare. By the time I got there, the bridge was up and the other car was going a mile a minute down the highway on the other side. Any excitement here?"

The boys told their father about the message Frank had picked up on the short-wave in the roadster, while Joe had heard the identical words from the mysterious truck.

"We thought it might have been sent by the factory watchman. Perhaps he has a transmitter."

Fenton Hardy strode off briskly toward his own car. ' * It 's time we checked up on this factory," he said. "Come on, Joe," he called, "I have a little job for you."

The detective took a suitcase from the bag' gage compartment. From it he removed a port-able typewriter, a pad of telegraph blanks, and some envelopes, as well as a suit of clothes and a cap.

"Put those on, son," he said to Joe, "while I write something."

With the portable typewriter on his knees, Fenton Hardy tapped out a brief message on one of the blanks, which he sealed in an envelope. In the meantime Joe was struggling into the suit. It was a messenger 's uniform.

"Where am I going in this outfit?" he asked in wonderment.

"To the factory office," said Fenton Hardy calmly. "This message is addressed to the manager. He isn't there, of course, but you will ask the watchman to get the manager's home address for you. I want you to get inside that office somehow, and find out what you can."

A few minutes later Joe walked into the factory courtyard from the highway, went boldly up to the office door and rapped sharply. There was no response. Joe hammered noisily. After a while a light gleamed, then the door was opened. A burly-looking man gazed at the boy suspiciously.

"What do you want?" he asked gruffly.

"Telegram for the manager," said Joe coolly.

"All right. I'll take it." The watchman reached for the message.

"Sorry. It has to be delivered to him personally."

"It's after hours. He's at home."

"Looks as if I made a long trip out here for nothing," grumbled Joe. "What's his house address?"

He was hoping that the watchman would not know it offhand. The guard thought for a moment, then said:

"I believe it's on Island Avenue, but I'll have to look it up. Just a minute."

As he walked off, Joe boldly pushed his way into the office. The watchman opened a desk drawer and began going through a file, looking for the address.

"Nice radio you've got," said Joe, motioning toward a handsome set on a table near the window.

"Fellow gets lonesome here at night. Programs help pass away the time," grunted the man.

The boy edged over to the set. He was a little surprised to find that it had no short-wave tuning equipment. If any messages were being received or transmitted, it was not over this instrument. Joe prowled around the office, his eyes taking in every detail of the place. Could a short-wave set be hidden--

Suddenly the watchman flung the file of address cards on the desk and lunged at the intruder.

"You're no messenger!" he shouted angrily.

Joe ducked. But the fellow was too quick for him. A pair of heavy hands gripped the Hardy boy's throat.

"I'll teach you to spy on me!" snarled the man, shaking Joe violently.

The youth struggled to free himself and tried to shout, but the strong hands were clamped tightly on his throat, choking him.

CHAPTER XIII.

THE LION CUB TALKS.

THE Hardy boys had not kept themselves in top form for nothing. As the factory watchman grasped Joe's throat, the agile youth suddenly squirmed and brought the side of his stiffened hand down sharply against the guard's neck. A thumb jabbed hard beneath the fellow's ear.

At the same instant, as the man yelped with pain, Joe twisted himself free. He sprang toward the electric switch and quickly snapped the lights off and on again twice. Long ago this signal had been arranged between the Hardy boys as a call for help, should one of them ever be in trouble.

"What do you mean, spying?" snapped Joe as the watchman glowered, rubbing his neck. "Have you a guilty conscience?"

The factory guard realized that he had acted too hastily.

"Forget it," the man mumbled. "I didn't like the way you was acting, that's all."

"And I don't like the way you're acting," declared Joe, following up his advantage. "Is that the way you treat every messenger who comes in here?"

Just then the door was thrust open. Fenton Hardy and Frank rushed into the office. They looked relieved to se& that Joe was unharmed.

"Say, what is this anyway?" demanded the watchman belligerently.

The detective flipped back Ms coat lapel to reveal his badge.

"Never mind asking questions. Just answer them," he snapped. " Where is the radio transmitter you've got hidden around here?"

"I haven't got any. No radio around the place except that one," grunted the watchman, indicating the instrument by the desk.

"Search the place, boys," said Mr. Hardy. "What happened, Joe?"

"He thought I was spying and tried to choke me."

His father picked up the telephone. " What's the name of the company president? And his phone number? Quick."

The watchman gulped, but supplied the information. Mr. Hardy dialed the number. "And your name?" he demanded.

"O'Markey."

"Well, O'Markey, I think we'll have your boss come down here. Too many queer things going on around this factory."

When the company president answered the telephone, Mr. Hardy spoke to him briefly but urgently, asking him to hurry to the place. Mystified, the official said he would be down in ten minutes.

While waiting for him, the detective sat on a corner of the desk and questioned the watchman shrewdly. O'Markey merely became sullen, and denied all knowledge of trucks, robberies, signals and short-wave sets.

The boys came in from their search of the other offices to report. They had found nothing.

"If there's any short-wave set around here, it's well hidden," said Frank, disappointed.

They again searched high and low through, the main office but with no success. O'Markey watched them narrowly. His expression became scornful and triumphant.

"I told you there wasn't no short-wave here. It's just going to be too bad when the boss gets here. He'll want to know what right you've got to come bustin' in here and--"

"Mr. Hardy has every right to come inhere," said the company president, suddenly striding through the open door. "If he thought there was reason to investigate this place, I'm very fortunate to have him know it."

Mr. Turner was a stout, peppery little man. He shook hands with the detective.

"What's the trouble, Mr. Hardy? Thieves? Burglary?"

He was told something of the evening's events. Without going into detail regarding his investigations of the Hudson gang, the boys' father told enough to convince Mr. Turner that the watchman's conduct had certainly been suspicious.

"O'Markey," he snapped, "I'm going to call the police and have you arrested. You know as well as I do that no truck deliveries are made here at night. What's been going on?"

"This is a frame-up," said the factory guard angrily. "I didn't see any trucks. I didn't send out any signals. You can't have me arrested because you haven't any evidence."

Fenton Hardy realized that this was only too true.

"So far we have nothing but suspicions," he said to Turner. "I doubt if the police would hold O'Markey on our say-so. And yet I'm absolutely convinced those truck drivers were getting signals from this building."

Over at the other side of the office Frank had been admiring a fine specimen of stuffed fox which stood on a bookcase. Upon examining the animal more closely, the boy gave a low whistle and called to his brother.

"Joe. Come here a minute."

Fenton Hardy, continuing his questioning of O'Markey, paid scant attention to what the boys were doing. But a few moments later his eyebrows flew up in astonishment when his sons carried the stuffed animal over and placed it on. the desk.

"May we ask where you got this fox, Mr. Turner?" asked Frank politely.

"It was a present. From Jim O'Markey, the watchman here," replied the company head promptly. "Why? Anything wrong?"

Frank manipulated a hidden spring in the base on which the fox was mounted. Slowly the animal divided into two halves. Inside was revealed a small transmitting and receiving set with a telescope type antenna.

"Well, I'll be hanged!" exploded Turner. "I guess I got more than I knew when you gave me that present, O'Markey."

"I didn't know there was anything inside the fox," mumbled the fellow sullenly.

"Oh, no?" The company president turned to Mr. Hardy. " I think this man should be handed over to the police and if you don't do it, I will." Then a sudden thought struck him. "But what am I going to do for a watchman tonight? I can't leave the place unguarded. Not now, of all times."

"I think I'd like to stay here for the rest of the night," said Fenton Hardy. " It's just possible that some of O'Markey's friends may drop In, and I'd like to be around."

"Shall Joe and I stay with you?" Frank asked.

"It won't be necessary," his father replied.

"Then we'd better go home."

The boy now told about Aunt Gertrude's message that a burglar had entered the taxidermy shop during their absence and taken a small stuffed animal.

"You'd better see about it," Mr. Hardy advised, and turned to the telephone to call the police. O'Markey was to be arrested!

It was midnight before the boys reached home. Aunt Gertrude, irate, met them at the door. .

"You don't care about your home at all, do you?" she said. "I tell you there's been a burglar here, and still you'stay--"

"We were helping Dad," said Frank quietly.

"Well, why didn't you say so in the first place? And where is he?"

Quickly Frank told her, then the boys went off to look at the taxidermy shop. As far as they could see, everything was in its place. In fact, everything looked just the same. Evidently Chet had done no work since they last had been there.

"Probably he was the person Aunt Gertrude saw running off," decided Joe.

The woman was greatly annoyed at her nephew's conclusion, insisting the fellow was a burglar and no one else.

"Mark my words, you'll find the whole shop cleaned out one of these days!" she prophesied.

To change the subject, Frank asked his aunt if she had enjoyed herself during the evening. She said she had been listening dutifully to the short-wave set in her brother's study.

"Fenton asked me to listen for clues on that special frequency, but I never heard such gibberish in all my life," she sniffed. " 'Not tonight. I'll let you know.' And a lot of cat howls."

"I guess you heard the same messages we did, "Frank told her.

"And somebody saying 'Help-Hudson'- whatever that may mean."

The boys were surprised. That was one message they had missed.

"When did you hear it, Aunt Gertrude!" Frank asked.

"About ten minutes ago."

This fact puzzled them because previously the strange words had always been heard before a robbery, and this had come after what the boys believed was to have been one at the battery factory.

"Maybe another robbery is going to break!" cried Frank.

He grabbed up a telephone and called the State Police. Orders went out to every station in the surrounding area for men to proceed at once to all factories making electronic equipment. Then Frank called the Bayport Headquarters, suggesting that patrolmen watch local stores selling radio parts.

The boys kept in touch with the police, but as had happened upon previous occasions, no attempted theft was reported. At Aunt Gertrude's insistent urging, the brothers finally went to bed at two o 'clock.

The next morning she awakened them to say that Chief Collig wanted them on the telephone. The officer had nothing to report, but he berated the boys rather briskly for getting out every policeman in the surrounding territory the night before. He himself had been in bed asleep when their summons had come.

"We'll round up this gang of thieves without your help," he boasted. "So don't bother to make any more suggestions to the Police Department-especially in my absence!"

Frank was disgusted at the man's attitude and told Joe so as soon as he had hung up.

"Never mind Collig," said Joe. " He likes us like poison anyway. You know that. Say, how about having a little fun with Chet?"

"How?"

Joe pointed to a small portable radio on a table. It was another new one his father had just purchased. Besides bringing in commercial programs, it also carried short-wave for both receiving and transmitting.

"O'Markey gave me an idea last night," Joe told Frank. "Let's take this to Chet's taxidermy shop."

"Why?"

"I'll show you."

The fat boy had not arrived yet, although he had promised to be there that particular day. On a bench by the window stood Chet's most recent purchase-a stuffed lion cub with a good deal of -the stuffing gone. Joe measured it with his eye. Then, grinning, he placed the small portable radio beside the base on which the animal was mounted.

"Just the right size," he murmured. "Let's get busy before Chet shows up."

Frank needed no further explanation. The radio was installed inside the baby lion, the connecting wire was carefully hidden and plugged into a wall outlet. A moment afterward, from the mouth of the cub, came the music of a string quartette. Satisfied that the trick would work smoothly, the boys disconnected the plug and awaited the arrival of Chet.

Their stout chum came clumping up the garage stairs shortly after ten o'clock. He was whistling softly to himself. Frank and Joe, who had hidden themselves behind some empty boxes, peeped out. They saw him take off his coat and settle down at the work bench. But he did not work; he just gazed out the window.

Frank slipped the plug into the wall outlet. Chet turned and scanned the room.

"Now where in heck did that thing go?" he said aloud.

He got up from the work bench and began prowling about.

"Couldn't have walked away," muttered Chet, puzzled. "That's very strange."

From the mouth of the lion cub came a brisk, cheery voice. "Do your hands still look attractive after you have washed the dinner dishes?"

Chet chuckled. "That's one on you, fella. I don't wash the dinner dishes. And as for my hands being attractive--"

Suddenly the fat boy jumped about six inches into the air and came down trembling.

"Holy smoke!" he cried out. "Who said that?"

"Do you get foamy suds in the dishpan?" asked the voice.

Chet took one horrified look. "Yippee! It's the lion cub!" he squalled. "Great guns-the animal's haunted!"

He wheeled and headed for the door, but stopped almost at once. He had heard another sound. The Hardy boys, unable to hold in any longer, had exploded with laughter. As for the lion cub, it said:

"I'll make your work easier for you, if only--"

Frank pulled out the plug, and the lion cub regarded Chet in dismal silence. Its owner sat down, glaring at his chums.

"Nice friends!" he said bitterly. " I suppose you think that was funny. What was the idea?"

"Can't you guess?" chuckled Joe.

"Now listen, fellows," said Chet. "I work most of the time, honest I do."

He was about to make promises for the future, when the boys heard footsteps on the stairs. Fenton Hardy came into the loft and said, "Good morning."

"Any luck on the case, Dad?" Frank asked him eagerly. The detective shook his head. "Nothing much. I got a report on that car I followed to the drawbridge last night. It was found abandoned in a field early this morning. It had been stolen. Any news here?"

"Yes, sir, there is," declared Chet suddenly. "My stuffed bear cub is missing. I can't find it anywhere. I think somebody broke in here last night and took it."

The Hardy boys looked solemn. So Aunt Gertrude had been right, after all. Frank had a hunch who the thief might be.

"Remember the man who stole the stuffed animals from the Suydam auction?" he asked.

"And the one who bought the stuffed wolf? Maybe he's the one who was here." Frank snapped his fingers. " And I have an idea about how we might locate him. It just came to me!"

"How?" asked Chet, wide-eyed and eager.

"Listen!"

CHAPTER XIV

ME. ZETTER's STORE

NOT long after Frank explained his hunch, he and Joe were standing in the electrical store next to Roundtree 's taxidermy shop.

"This old radio of ours has been acting up lately, Mr. Zetter. Could you fix it for m>?" Frank asked the proprietor, setting the box on the counter.

The man scowled at them over his spectacles. "I got more work than I can handle now," he said ungraciously. "Leave it here if you like, but I probably won't be able to get around to it for a week or more."

"We'll leave it, anyway," said Frank.

While he was explaining what he thought was wrong with the radio, Joe ambled toward the rear of the store, innocently examining every detail of the place. He was close to the basement steps when Zetter called out sharply:

"Stay away from there!"

"You mean the steps?" asked Joe in surprise.

"Yes." The proprietor came around the counter and kicked shut the trap door above the stairway. "All right, if you boys haven't any more business here, I'll get on with my work.

I've got a lot to do."

"'What you need is a helper," said Frank.

"I don't want any man around here," replied Zetter; then added quickly," I could use a young boy part-time, though."

"We may be able to get you one," offered Frank quickly. "He could watch the store and make deliveries for you."

"Send him around. I'll talk to him."

The Hardys left. Their visit to Zetter's place Iliad been the outcome of Frank's hunch that by some long chance Chet's stolen bear cub might be in the cellar of the store. The boys found the alley door to it locked, so- they were not able to prove whether Frank's theory was right or not. They agreed that Zetter was not a very pleasant individual and would bear watching.

"What did you mean by telling him we could get him a boy to help in the store!" Joe asked his brother.

"Maybe Jimmy Gordon would like that job. And while he's working for Zetter, he can have a look at that basement-for us!" said Frank with a grin.

"Good idea, unless there should be a connection between Zetter and Jimmy's Uncle Elly Batter," observed Joe shrewdly.

"You're right, I hadn't thought of that. Let's go to the Gordons' and broach the subject to them. Maybe we'll find out something."

When they called at the Gordon flat and told Jimmy they had found a job for him, the youngster was delighted.

"Is it all right with you, Dad?" he asked.

"Somebody will have to make a living for the family," said Mr. Gordon, who was lying on the couch with his ankle swathed in bandages* I 'Where is it?"

As Frank replied, the Hardys watched the three Gordons narrowly. At the word Zettor, they showed no change of expression, however, so the boys concluded Joe had been wrong in his supposition that there might be a connection between him and Elly Batter.

"Can I start work right away?" asked Jin any enthusiastically.

"Sure can," smiled Frank, following the lad to the hall. He whispered to him, "Be careful you don't run into any wolves in the cellar, though."

Jimmy recalled the incident of the stuffed wolf and chuckled.

"And let me know," Frank added, "if you see any other animals down there!"

"I'll keep a sharp lookout," the youngster promised, and dashed off down the stairs.

When Frank returned to the flat, Joe was speaking to Mrs. Gordon. "Have you heard from your brother since he moved?" he asked, hoping to learn something about Elly Batter.

"He isn't my brother. Just a brother-in-law," said the woman. "We haven't seen Elly Batter lately."

The Hardys thought they detected an uneasy exchange of glances between husband and wife.

"Owns a radio factory, I believe," stated Joe;

Mr. Gordon laughed scornfully. "Jimmy probably told you that. He doesn't know -what he's talking about. Elly doesn't know any more about electricity than I do. He works in a tannery. Skiffin Brothers Tannery, two blocks from here."

The boys did not pursue their inquiries any further, for they did not want to make the Gordons suspicious. But upon reaching the street a few minutes later, they headed directly for the tannery. At the time office they inquired about Elly Batter.

"Doesn't work here any more," said the time-keeper. "He got fired. Absent too much. Didn't show up for work three days out of six."

"He worked at night sometimes, didn't he?" asked Joe, recalling what the woman at the apartment house had said.

"No, he was on the day shift. That is, when he showed up," added the timekeeper, turning away.

Since there was nothing more the boys could learn about Elly Batter at the tannery, they went home. Joe was not satisfied to let the matter drop, however. Elly Batter had been dressed in working clothes the night Joe had seen him on the bus. Could it have been that the fellow had another job in the evening, and the daytime job was only a blind? This might explain why he was absent so often from the Skiffin Brothers plant.

Joe was still trying to figure out the puzzle that afternoon while helping Chet in the taxidermy shop, when Jimmy's young friend Mickey stumbled up the stairs, flushed with excitement.

"Jimmy can't come here any more," he reported. "He told me to tell you."

"Who said so? What's the matter?" asked Frank. This was a new turn to things.

"His father. Mr. Gordon gave him an awful licking because Jimmy talked to you about his Uncle Elly. And now his Dad says he can't come here any more."

The Hardy boys were surprised, and they felt bad too that the lad had gotten into trouble at home on their account. Frank was about to suggest that he and Joe go to the Gordon home to try to straighten out matters, when Mickey remembered the rest of his message.

"Oh, yes, and Jimmy said to tell you there isn't any wolf in Zetter's cellar but there are all kinds of other stuffed animals that scared him. And I saw them too," added Mickey proudly.

"Did you notice if there was a bear cub?" asked Chet quickly.

Mickey nodded. "Sure. I saw a cub. But it isn't there now. None of them are there now. Mr. Zetter packed them ail in a big box and took them away in a car."

Mickey, little realizing the importance of his message, fell to watching Chet mix clay to mold artificial cheeks, forehead, and muzzle for the deer. The Hardy boys went downstairs to talk over what they should do.

"Something queer about Zetter, all right,"" said Frank. He looked at his watch. "We just have time to go downtown and see Roundtree before he closes."

"Why Roundtree?"

"He's a taxidermist. And his store is next to Zetter's place. Maybe the two are working some sort of game together. Let's go and ask Roundtree a few questions."

But after talking to old Mr. Roundtree, the boys felt pretty sure he had nothing to do with, any work of a suspicious nature. Just the same, their casual questions to him brought out some interesting information. Yes, the taxidermist said, he had been unusually busy of late, and had made a good many sales of stuffed animals.

"Business seemed to perk up all of a sudden the last couple of weeks," he said innocently. "Sold a stuffed bear the other day. Also a fox."

"To the same person?" asked Frank.

"Oh, no. Strangers to me. Man who bought the fox said he was a watchman." Mr. Bound-tree looked at his watch. "Closin' up time. Anything I can do for you boys?"

"Not today," they told him and left the store.

On their way home Frank said he thought the man who bought the stuffed fox was probably O'Markey. Joe suggested they borrow a photograph of the watchman from the police and show it to the taxidermist in the morning.

"If he can identify 0'Markey, it might prove a good day said Frank.

Accordingly they stopped in Headquarters and made their request. The sergeant on duty said he would try to get a copy of the police photograph of O 'Markey for the Hardys.

"Drop in for it tomorrow," the officer said.

When the brothers reached the street, Frank suggested they step lively.

"Aunt Gertrude said Professor Wood is coming to dinner. He's probably there now, and we 're expected to entertain him until Dad gets home."

But when they reached the house they found that neither Fenton Hardy nor Professor Wood was in evidence. Aunt Gertrude, who had given special attention to the dinner, was walking around, flushed and exasperated.

"That's men for you," she declared. " Can't depend on them."

"They'll probably be along any minute," said . Joe soothingly. "Dad likely picked up Professor Wood in his car--"

"Professor Wood was here half an hour ago, waiting for your father," said Aunt Gertrude tartly. "But now I can't find him. And your father, who invited him, hasn't shown up at all. "

The telephone rang. Frank answered it, thinking it might be one of the men. But the voice on the line was that of a girl.

"Hello, Frank. This is Iola Morton. Will you please tell Chet to come home at once? He's going to be awfully late to dinner, and Mother wanted to go out early."

"Not usual for Chet to be late to dinner," chuckled Frank. "I'll chase Mm right home, Iola."

The Hardy boy hurried toward the garage, thinking he knew why Chet was still in the shop. Professor Wood probably had gone out there and the two were discussing taxidermy. It was even possible the good man was listening to a lecture by their chum!

But Frank saw no lights and heard no voices as he mounted the stairs to the big room over the garage. The door of the taxidermy studio stood wide open. Apparently his fat friend had gone away without closing it, and Mickey had left with him.

Frank was about to turn around and descend, when in the dim light he caught sight of a paper tacked to the door. He went up the few remaining steps to read it, and then caught his breath as the full import of the printed words dawned upon him.

HARDYS

YOUR FAT FRIEND WILL NOT RETURN

UNTIL YOU LAY OFF YOUR DETECTIVE

WORK

CHAPTER XV

"BY THE OLD MILL STREAM"

Frank flung open the door and raced to the front window of the taxidermy shop. He called to Joe at the top of his voice. A moment later his brother appeared at the back door of the Hardy home.

"What's up?"

"Come here. Quick!"

Joe rushed across the yard. In the meantime Frank looked around the studio. There were indications of a struggle; a bench had been upturned, and tools lay scattered on the floor.

When Joe read the warning message, his first thought was to call the police. But Frank was not so sure this would be wise.

"The note says our fat friend won't return until we lay off," he pointed out. "After all, if Chet has been kidnapped, it might be the worst thing we could do--"

"Listen!" said Joe suddenly.

From in somewhere in the garage loft the boys heard a faint tapping. It died away for a moment. Then they heard a distinct thump, thump.

Frank wrenched open a door that led to a storage space at the back of the loft. Now the tapping was clearer. It seemed to come from a closet at the far end of the room-a closet ordinarily used for storing tools and garden implements. The door to it was closed.

The knocking became louder, as the brothers rushed forward. The door was locked and the key was missing. Joe snatched up an iron bar from a corner, and together the boys pried the door open.

"I'll bet it's Chet!" said Joe, as the hinges creaked and the lock snapped.

But when the door flew open, out stumbled not Chet, but Professor Wood, bound and gagged. If the boys had not caught him in their arms, he would have fallen to the floor.

Hastily, they untied the ropes and removed the gag. Professor Wood, although shaken by Ms experience, was otherwise unharmed.

"Thank goodness, you heard me," he said. *' I might have smothered in there."

He told them what had happened. While waiting for Fenton Hardy to arrive, he had decided to visit the taxidermy studio but had found no one around. He had been about to leave, when someone had come up behind him suddenly.

"I was blindfolded, gagged and bound. Then. the fellow dragged me to the closet and locked me up. A little while ago I managed to slip the handkerchief off my eyes, but that was all I could do."

"Did you see who did it?" Joe asked him.

"No, I didn't. In fact, I don't know whether it was one man or more than one who attacked me," confessed the professor ruefully. "But why did it happen?"

The boys had their own ideas, but did not tell the elderly scholar. It seemed likely that Chet already had been kidnapped by the time the professor had arrived at the loft. The abductor, while printing the note, had been surprised at his work by the scientist, whom he had removed in a hurry.

"We'd better talk to Dad about this," Frank said tersely. "Professor Wood, please don't say anything to our Aunt Gertrude about the attack. It'll upset her."

The elderly man agreed. The boys took him to the little washroom in the garage, where he refreshed himself before going to the house. Mr. Hardy still had not returned when they got there.

"I can't understand it," said Aunt Gertrude. "But then, living in a detective's home is a mighty uncertain thing at best."

Miss Hardy decided to go ahead and serve dinner. It was an uneasy meal, for her nephews kept worrying about Chet. Were the criminal activities of the Hudson gang creeping closer to the very threshold of the Hardy home?

Aunt Gertrude noticed that something was wrong. She remarked that the boys were unusually silent, and wanted to know why the professor seemed lost in thought.

"The fact is," said the scientist, "I had hoped to talk to Fenton at dinner tonight and ask his advice about organizing a party to search for my friends. I believe their plane might have been forced down in some out-of-the-way place. They may need help."

Miss Hardy was sympathetic and urged him to wait a while after dinner was over, but Professor Wood declined. If the detective were detained because of work on a case, there was no telling when he might be in. So the good man took his hat and cane and departed. Frank and Joe managed to talk to Mm alone a few moments on the porch steps, saying they would speak to their father about the attack on the professor as soon as he should come in.

"Shouldn't I tell the police about this outrage?" asked the scientist. "After all, those thugs might have killed me."

"Will you leave that to us, sir?" suggested Frank. "You see, there are a great many things mixed up in a mystery our Dad is working on. You can depend on it, we're just as eager to find out who attacked you as you are."

"Very well," said the elderly man dubiously. "It seems very irregular, though."

When the professor had gone, the boys telephoned to the Morton home. Learning that Chet had not returned, the Hardys debated whether or not to tell his parents about the warning note. They decided against it for the time being, although the brothers knew they were taking a heavy responsibility. They went back to the taxidermy shop to look around again in the hope of finding some clue to the mystery of their fat chum's disappearance.

They found nothing to help them, but did discover that the lion cub with the portable radio inside it was missing. Had it been stolen? Or had Chet taken the instrument with him?

"If he did, maybe he'll try to communicate with us," said Frank hopefully. "Let's see what we can pick up on short-wave."

"Suppose I try getting a message through to Chet on the transmitter in Dad's study," suggested Joe. "You listen to our frequency on the living room radio. If we don't find out anything in the next hour, we'd better let Chet's people know and turn the case over to the police."

For the next thirty minutes Joe sent out a constant call for K2XOB, in the faint hope that their chum might be within earshot of a shortwave set. Frank, on the other hand, kept listening for a message from Chet. There was not a sound for a long time, then suddenly he heard a voice, muffled and distant.

"Frank and Joe-Frank and Joe."

It was smothered by static, but Frank caughs enough to be reasonably sure it was Chet trying to reach them. Excitedly Frank tuned the instrument more finely. The static stopped, Then came the voice again, this time singing in a nervous, cracked voice:

Down by the old mitt stream Where I first met you--

Then silence. Frank called to his brother, who came rushing in at top speed. For five minutes the Hardys waited patiently for a repetition of the words, for they were sure it was a signal of some kind from Chet.

Aunt Gertrude came into the room. "What on earth is going on around here?" she wanted to know. "There's something mighty mysterious--"

Suddenly the cracked voice on the radio sang out:

"Aunt Gertie, get your boys, get your boys, and we'll all sing Down by the Old Mill Stream!"

Aunt Gertrude glared. "Well, I never!" she exploded. "Somebody making fun of me!"

"I 've got it!" whooped Frank. " The old mill stream! I know what Chet's trying to tell us. The old mill! Remember?"

Months before, the Hardy boys had encountered danger and excitement in solving a mystery that centered about an old mill near the falls on Willow River. This fact was well known to Chet, who had accompanied the boys on some of their excursions to it. If he were trying now to convey a message that would be meaningless to anyone else who might be listening in, this would be an ideal subject for him to use.

"Now look here," said Aunt Gertrude, "what does this all mean! Who is trying to tell you something about what? And what's this about the old mill?"

"Sorry, Aunty, we'd rather not tell you until We're sure," called back Frank as the boys dashed from the room. "We have a job to do."

They raced from the house and got into their car. A few minutes later the brothers were heading toward the boathouse which sheltered the Sleuth. Soon the fast motorboat was cutting across the waters of Barmet Bay. While Frank steered the craft, Joe turned on the radio, hoping to pick up another message from Chet Morton.

When none came, Joe switched to the mysterious frequency which the Hardys thought Hudson was using. By this time the boat had crossed the bay and was proceeding up Willow River. Suddenly the set blared forth with an astonishing medley of sounds just like a riot in a chicken yard. A rooster crowed, hens cackled and squawked. It was much louder and more urgent than the cat-and-dog fight and other animal noises the boys had heard previously.

"The warning signal?" suggested Frank. "Another robbery?"

The Hardys were in a quandary about what to do. Should they abandon the search for Chet in order to follow up this new lead?

"We'd better find a phone and call the State Police," decided Joe.

Through the gathering darkness they caught sight of lights in a farmhouse on the river bank. Swiftly Frank swung the wheel, heading the Sleuth toward a small dock at the foot of a path leading to the house. The boys jumped out.

The farmer who opened the door in answer to their knock readily agreed to let them use the telephone. But when he overheard them telling the State Police their suspicions that another robbery of radio equipment was being planned, the man exchanged uneasy glances with his Wife.

"Hope nobody is going to blow up any of the factories around here," he said to the boys. "Sounds like you fellows figure there's going to be some trouble."

"I didn't know there were any factories around here," remarked Frank evasively.

"There's a kind of secret one in the woods just back of this farm," said the man. "And another across the river, about a quarter of a mile upstream, just this side of the old mill. It's a new one; branch of the Austin Engineering Company, accordin' to what I heard."

A new factory near the old mill! The boys had thought Chet was near the mill. But maybe he was being held a prisoner somewhere else and had overheard the plans for a robbery at the spot!

"Thanks for the use of the phone, sir," said Frank hastily. " Don't worry. There probably won't be any trouble around this neighborhood."

The boys hurried outside and went off in the Sleuth. Presently Frank remarked they must be nearing the factory, and a moment later the brothers saw the dark outline "f the new building. Down near the shore a light twinkled briefly, then went out.

"Someone on guard, maybe," said Joe.

To avoid detection, Frank continued upstream for a short distance beyond the factory, then he swung the boat around, cut the motor, and let the Sleuth drift back silently with the current. A glimmer of moonlight filtering through the clouds showed him a small wharf below the factory. As the boat neared it, Joe threw a rope around a post on the dock and tied the craft fast. He and Frank stepped out noiselessly.

Stealthily the boys made their way up the slope. Suddenly, against the moonlit sky at the top of the incline, they spied a shadowy figure. It moved forward in a crouching position. There was something sinister about the way it proceeded. The boys crept closer.

Without warning, the figure straightened up and lunged ahead, raising an arm. At the same instant the moon came out brightly, revealing another man just beyond. Fenton Hardy! He was standing motionless, completely unaware of the assailant who was about to strike him down I

CHAPTER XVI

CHET 'S BIG ADVEISTTUBE

THE Hardy boys were too far away to grab the would-be assailant. But they were not too far away to warn their father. Both Frank, and Joe yelled.

The upraised arm swooped down sharply, but the blow went wild, for at the shout Fenton Hardy ducked to one side. For a moment the two figures were locked in struggle. Then the attacker broke away and came stumbling down the slope toward the Hardy boys.

"I'll tackle him!" shouted Frank.

He dived, locked his arms around the man's legs, and brought him crashing down. Joe pounced on the man's shoulders. The brothers were about to drag their struggling prisoner to his feet, when their father came running toward them.

"All right, boys. I'll take care of him!" he said.

Mr. Hardy and his well-trained sons gave no sign of recognition, although all were astonished to find the others there.

"Looks as if we got here just in time. This fellow was going to slug you," said Joe.

"Let's have a look at him."

Mr. Hardy whipped a flashlight from his pocket. He turned it full on the prisoner's face.

"Why, he's the man who drove the stolen car the day of the Suydam auction!" exclaimed Frank.

"You know him?" asked Mr. Hardy.

""We don't know his name, but we certainly know his face," Joe assured his father.

"Listen, you fellas got nothin' on me," growled the man. "I was just out for a walk, see, and I thought you was a burglar. Lemme go."

He gave a sudden wrench in an effort to break free, but Frank had a wristlock on him. The fellow gave a yelp of pain and subsided.

At this moment someone else came floundering down the slope. Mr. Hardy turned the flashlight up the hill. Into the circle of light came a stout figure clad in dungarees and a jersey. Chet Morton!

In spite of Frank's and Joe's astonishment at seeing Chet Morton safe, they did not show their surprise. But they kept wondering how their chum had got there and why he was clad in the garb of a riverman.

"Hello, fellows," piped up the stout boy. "Gee whiz, I'm glad to see you. I was helping your--"

"All right. Let's take this fellow up the hill to the factory," interrupted Mr. Hardy. He gave Chet a warning glance. Apparently he did not want him to talk so freely in front of the prisoner.

Frank took care of the captive, while Fenton Hardy, Chet and Joe went ahead. On the way the detective quietly told his younger son what had happened. He had returned to the Hardy house in order that his boys might accompany him on a surprise visit to the Austin plant. Since they were not at home, he had asked Chet to come along to interview the watchman at the factory.

"I didn't dare do it myself," he concluded.

"You suspected trouble here?" asked Joe.

"Yes, I had a good tip this factory is on the Hudson list and I wanted to do some checking up before any of the thieves might come to make a haul. Did you find out anything from the watchman, Chet?"

"Couldn't locate the fellow. All the doors were locked and he didn't answer my knocks. But maybe he couldn't hear me. There was a radio going inside."

"What was on it!" asked Joe quickly.

"Music."

Joe was disappointed. For an instant he had hoped the set might have been broadcasting some of the strange programs the Hardys suspected were Hudson's signals.

By this time the three had reached the top of the slope. The prisoner was lagging behind, but Frank was prodding him on. While waiting for them, Joe told how the brothers had picked up Chet's singing of Down by the Old Mill Stream on their radio.

"It was your father's idea," explained the stout boy. "He put--"

"Sh!" warned Mr. Hardy. " Here comes the prisoner. You can take off that riverman's disguise now if you want to."

"Thank goodness," said Chet in relief. He began peeling off the jersey. "I'm not so sure I like detective work. It keeps a fellow nervous. " He looked apprehensively at the shadows of the trees in the moonlight. "I sure thought I was a goner when I lost you, Mr., Hardy." Then he turned to Joe. "Say, when are you fellows going home? I haven't had any dinner yet." For Chet this was an extreme calamity.

"You aren't going home," said Mr. Hardy. "I want you to guard the prisoner while my sons and I have a look around the factory."

Chet groaned. "I knew there'd be a catch in it," he said woefully. "Gee whiz, I'm going to cave in pretty soon if I don't get some food. After all--"

He interrupted himself at the sound of an approaching car. For an instant everyone stood alert. Were thieves arriving to pull a job at the Austin factory?

As the sound drew rapidly nearer, the Hardys hid behind trees, dragging their prisoner with them. But Chet was not quick enough. As the automobile rounded a bend in the roadway leading to the factory, its headlights shone full on the stout boy. The car skidded to a stop. Two figures leaped from the back seat.

"I'll nab this one! You look around!" ordered a voice.

Mr. Hardy plunged toward the two men, who they now could see -wore the uniform of State Troopers. He spoke to them quickly, explaining who he was, and added:

"Here's a prisoner for you."

The officers, upon hearing the stranger had tried to attack the detective, took charge of him at once.

"Gosh!" exclaimed Chet, "I can't make head nor tail of things. What made you troopers come here?"

"We had a phone call from the Hardy hoys, and--"

The office door of the factory opened. A man came toward the group, swinging a lantern.

"What's going on out here!" he demanded. "I'm the watchman. Nobody's got a right to come on this property without a pass." Then he noticed the policemen. " Oh!" he added, his bravado gone.

The watchman and the fellow who had tried to attack Mr. Hardy were now face to face in the glare of the car headlights. Frank and Joe thought they detected a glance of recognition between the two-a glance of bewilderment and alarm. But the men gave no other sign of knowing each other.

While the watchman was talking to the officers and Mr. Hardy, Frank at a sign from his father slipped into the shadows and entered the building. By a light which was on in the office he was able to make a quick survey.

As the boy looked around he suddenly heard a quiet voice speaking. Frank traced it to its source-a small room where stationery and files were stored. On top of a cabinet stood a radio. It was tuned to the same short-wave frequency on which he and his brother had heard the cat-and-dog fights and the barnyard imitations.

The voice had died away. Frank listened, but he heard nothing except the faint hum of the set. Then suddenly there came a distinct but weak voice. It said:

"Help! Hud--"

Then it broke off. The boy waited as long as he thought advisable to stay away from the group outside. But no further sounds came over the air.

As soon as he emerged from the building he spoke to his father. Mr. Hardy asked two of the officers to drive off with the prisoner, and the other two troopers to remain on guard at the factory and keep track of the suspicions watchman.

"Nothing more we can do here," said Mr. Hardy to the boys. "You'd better drive home with me in the car, Frank. It's parked down the road. Joe and Chet can take the boat back."

"Well, sir," beamed Chet, cheerful now that the prisoner was off his hands and dinner was a possibility, "this has certainly been a big adventure for me, but I'm glad it's over."

"You'll never know how surprised we were to see you." Joe told him. "Don't you know you're supposed to be kidnapped?"

"Kidnapped!" gulped Chet, turning pale.

Joe told about the note tacked to the door of the taxidermy shop. The stout boy turned several shades whiter, and Mr. Hardy looked grim.

"Oh, gee, don't tell me there's a gang of kidnapers on my trail!" Chet moaned. " I think I ought to take a long vacation, don't you, Mr. Hardy? I'll start tomorrow!"

The Hardys, knowing Chet as well as they did, were sure he would do nothing of the sort. Instead, he would come right back to the taxidermy shop. But they knew he would be wary nevertheless. Everyone tried to guess who had put up the note, but the kidnaper's identity remained a mystery.

On the way home in the car Frank spoke about the radio set in the factory office, which had been tuned to the same frequency on which had been heard the strange animal sounds and the Words " Do-r e-mi-don't-delay-so-land-the-do."

"So far as I can learn," said Mr. Hardy, "no short-wave station or ham in this part of the country has been awarded that band."

"Maybe Joe and I ought to make a real try at locating the place it's coming from. I feel pretty sure Spike Hudson is sending out the strange broadcasts as signals."

The detective was dubious about locating him by this method. "I'm afraid the man doesn't stay in any one place very long. Racketeer Hudson moves around a good deal. It's even rumored that he has a plane for making quick getaways." Suddenly Mr. Hardy snapped his fingers. " The lion cub! I forgot it!"

"What lion cub?"

"The one you boys put a radio in to scare Chet. We brought it with us and hid the cub in a tree trunk along the road."

"Chet got in touch with us on that transmitter?" asked Frank.

Mr. Hardy nodded. He backed the car around and they drove down the road. Near the lane leading to the factory ho stopped and got out. After searching for a vncment in a tree, he called out tensely:

"It's gone!"

CHAPTEB XVII

THE SECRET FACT

FAB from being dismayed by the loss of the lion cub, Fenton Hardy felt that it might turn out to be a break for them in solving the case. One thing was sure: neither the watchman nor the detective's attacker had taken it, as a search with the troopers proved. Someone else who had been spying was the guilty person.

"That stuffed animal can be traced," said Frank's father with determination, as the two drove home. "Tomorrow I'll ask the police to check with the heads of all factories making electronic equipment in this area to see if any of the workmen has a newly acquired stuffed lion cub."

"Haven't we made any progress at all on the case?" inquired Frank in disappointment.

"The police tell me that the number of robberies in factories making radio parts has decreased," his father replied. "They give us credit for that. But a lot of instruments made of stolen materials are still coming out. So far I haven't been able to discover where they're being manufactured."

When the detective and his son reached home, they found Professor Wood and Aunt Gertrude in the living room. The scientist, still worried over the attack on him in the taxidermy shop, had returned to get the detective's slant on it. After he had accepted his old friend's apology for failing to show up to dinner, and having satisfied himself he was in no danger from kidnapers, the professor leaned forward in his chair and said intently:

"Fenton, I have a proposition to make to you. It's about this search for my friends. If they are not located within a week, I'm to be allowed the use of an airplane and a pilot to continue the search. Now, I'd like company on the trip, as well as help. How about letting your boys go with me?"

Frank's eyes gleamed with excitement at the prospect. Mr. Hardy seemed a little doubtful.

"I'm not sure what their mother would say about it," he told the professor. "Suppose I get in touch with her in the morning. If she thinks it's all right, I'll give my permission."

At that the matter rested. The scientist departed for the second time that evening. Soon afterward Joe came in and upon hearing the news gave a shout of joy. Finally at Aunt Gertrude's insistence the family retired, but not until after she had made it plain she was not in favor of her nephews going on the proposed trip.

"Gallivanting off again!" she sniffed. " And goodness only knows where you'll land. In the midst of some head-hunters or in shark-infested waters or-" She closed her door firmly.

The next morning a special delivery messenger arrived early with a package for Mr. Hardy* He promptly took it into his study to open, then called in his sons to look at the contents. On the desk stood a new radio of a type they had never seen before. The boys whistled in admiration.

"Where did you get it, Dad?"

"Is it military stuff?"

"A million dollars couldn't buy one of these on the open market," smiled Mr. Hardy. "Government officials have allowed me this one for our work. It's a walkie-talkie of the very latest type with a secret feature."

Frank and Joe examined the set. It was very compact and well made, and could be tuned to any frequency. Its transmitting and receiving ranges were considerably greater than those of any other walkie-talkie yet revealed to the public.

"It may be the weapon that will smash the Hudson gang," continued Mr. Hardy, tuning the set to the frequency on which they had heard the suspicious sounds upon several occasions. "By the way, did you boys have any plans for the morning?"

"If you have no assignment for ns," replied Frank, "we thought we'd investigate that small factory the farmer told us about last night-the one he said is back of his place. *'

"A good idea," his father approved. "Go ahead."

Before departing, the brothers decided to run out to the taxidermy shop and leave a note for Chet. To their surprise the door was open and the stout boy was already at work.

"Thought you were going away on a vacation," Joe teased him. "Bather be kidnapped eh?"

Chet ignored the gibe. Instead, he turned away with a smile and reached under his work table. Instantly there came the ear-splitting shriek of a siren. The Hardy boys jumped in fright.

"What the-" began Frank.

Chet pretended not to have heard the sound. Looking innocent, he inquired what on earth was the matter with his friends.

"All right," laughed Joe. "We're square now. So this is how you're going to call for help if a kidnaper comes around."

"Or a burglar," added Chet proudly. " Close that door and then open it again," he directed.

Frank did so. The alarm which the stout boy had rigged up shrieked its warning again. At the same instant excited voices could be heard on the stairway. Aunt Gertrude and young Jimmy Gordon appeared, breathless.

"What's the meaning of this?" the woman demanded, looking from one boy to another.

Chet turned scarlet. He did not dare tell why he had set up the siren. Aunt Gertrude began to scold him, saying it was bad enough having a lot of stuffed animals and smelly chemicals around without disturbing the whole countryside.

Frank and Joe looked at each other. This really ought to help their chum out of his embarrassing predicament, they decided. To change the subject, Frank said loudly to Jimmy:

"What are you doing here? I thought your father wouldn't let you come to our house any more."

"Well-Pa-that is-" Jimmy faltered.

"You mean you came without permission?"

The youngster nodded. "Don't send me away. I like it here. You fellows have been nice to me. It's more fun here than hanging around the streets."

The Hardy boys scarcely knew what to do about Jimmy. They did not want to encourage him to disobey his father, yet they knew that if they turned the lad away he probably would get into difficulties with the police again. Before they replied, Aunt Gertrude spoke up.

"Well, Jimmy, I'll see that you don't get into any trouble here. This place," she said, giving the shop a deprecatory glance, "could stand a good, thorough cleaning."

While Jimmy was sweeping the floor, Frank asked him about Elly Batter. "How is your uncle? Have you seen him lately?"

"He never comes to our place any more. Ma says he has lots of money now and lives in a swell big house, but he didn't say where it is!"

Frank and Joe exchanged glances. This news certainly would bear investigation!

But in the meantime they would run out to the small secret factory the farmer had mentioned, since it had occurred to the boys that it might be

the place where Elly Batter worked at night-• the factory he claimed to own.

Before leaving Bayport, the boys stopped at Police Headquarters and were given the promised photograph of O'Markey, the guilty watchman from Turner's battery factory. They carried it to Mr. Roundtree, who promptly identified the face as that of the man who had purchased a fox from him. As the boys left his stop, they grinned in delight. They definitely were on Hudson's track!

"And now let's hurry to the secret factory," said Frank.

Although the building was located less than two miles off the highway, the Hardys had a difficult time finding it. The factory, hidden •deep in the woods several hundred yards back from an overgrown lane, was a small, frame structure cheaply and hastily put together.

There was no sign of activity about the place. After looking at it from the shelter of the trees for a while, the boys came to the conclusion that it was deserted; for the time being, at any rate. They ventured out of hiding and went forward.

Frank tried the door, which proved to be un= locked. It swung open loosely.

"Empty!" he exclaimed.

The building was indeed empty. There was neither machinery nor tools; nothing but four walls, a floor and a roof.

"The owners have skipped out," the boy decided.

"Perhaps the place has just been built," Joe suggested. "Maybe work hasn't started here yet."

Frank took a magnifying glass from his pocket and knelt down beside a small heap of rubbish near the door. He picked up a tiny metal screw, then examined a scrap of wire and other odds and ends.

"Radio material, I'm sure of it," he announced.

The boys searched the building thoroughly and examined the ground outside. Near the spot where they had parked their car Joe discovered tire marks in the dirt leading in the opposite direction from the one by which they had come. The impressions were fairly recent; made within the past two days, they figured.

The boys got into their car and cruised slowly along the road, following the tracks. The lane curved, finally meeting the highway. Here the marks became lost, although the curve of the tire treads indicated that the automobile had turned toward Bayport.

Joe sighed. "Another wild-goose chase," he said. " Well, let's go on to--"

"Look!" cried Frank, interrupting him.

He had spied an object in the grass at the side of the road. Jumping from the car, he stooped to pick it up. Although to a casual observer it was nothing more than a man's handkerchief, the Hardy boys had learned to follow up every possible clue, no matter how unpromising.

This time they were rewarded, for as Frank raised the handkerchief from the ground, a torn scrap of envelope fell out. The postmark on it was Bayport, and the address was Andrew Smith, Old Creek.

"That name Andrew Smith is familiar," said Frank excitedly. "Wasn't it the one Elly Batter used when he rented that apartment in Bayport?"

"It sure is," agreed Joe.

He too got out of the car and looked around His eyes caught sight of a dirty piece of paper in the near-by ditch. Obviously it was part of the letter the envelope had once contained. Only a section of one sentence was left.

"-have lots of material ready for you. S. H."

"When the Hardys read the initials the same thought occurred to each of them.

Spike Hudson!

"Let's hurry to Old Creek and find out about Andrew Smith," Frank urged. "Maybe we've tracked down Elly Batter's hiding place at last!"

"And can get a really good clue to that crook Hudson!" added Frank.

Old Creek was a tiny village on a stream running into the Willow River, about two miles away. It consisted of three houses and a general store which also held the post office. When the boys reached the place, they decided not to make the postmaster suspicious. Instead of broaching the matter at once, they bought several things, gradually leading up to the subject of Andrew Smith. The postmaster rubbed his chin thoughtfully.

"I don't know much about that fellow Smith," he said. "Stranger. Comes in here once in a while for his mail, but to tell you the truth, he never said where he lives. Nobody around seems to know anything about him either."

"When was he here last?" Frank inquired.

"Why, early this morning."

As the boy was about to ask another question, Joe nudged him and indicated the top of the old-fashioned roll-top desk which stood just beyond the postal window. On it was Chet's stuffed lion cub!

CHAPTEB XVIH

A CHANGE OF ADDBESS

FBAN.K and Joe had all they could do to keep still at what they saw. Of course, they might be wrong, but Chet's stolen lion cub had had an imperfection in its side, and the stuffed animal on the postmaster's desk had the very same imperfection.

"Would yon mind telling us," asked Joe, trying not to seem too curious, "where you got that stuffed lion cub? It's a pretty nice one."

"Got it from the fellow you were just asking about," the man replied. " Andrew Smith. He sold it to me cheap this very morning."

"Does it talk?" inquired the Hardy boy.

The postmaster looked at Joe as if he thought the boy was a little unbalanced mentally.

"Of course not. This isn't a toy. It's a- it's a collector's piece!"

The storekeeper took down the animal for the youths to look at. On closer examination they saw that it was indeed Chet 's missing lion cub, but a good deal lighter than formerly. The radio had been removed from it! The Hardys said nothing about this to the postmaster who, they felt sure, was innocent of any connection with the theft. They merely thanked the man and left the store.

"Gee, that was a bit of luck!" cried Joe. " So Elly Batter took the cub from the tree last night! What do you think we'd better do now?"

"Report to Dad. Nobody here knows where 'Andrew Smith' is, and it may be days before he'll come to this place again. Perhaps Dad will want to have one of his operators watch the store."

When Fenton Hardy heard his sons' story, he congratulated them on their morning's work and said he would send a man to Old Creek at once to shadow "Andrew Smith" if he should show up.

"It may put us on the right track," the detective said. "I admit I haven't been able to make much progress on the Hudson case," he added in a discouraged tone. "It's very baffling. It seemed at first as if the tip I'd had about the man using short-wave in his work was going to effect a quick solution. But it hasn't"

"The place from which he sends messages hasn't been found?" Frank asked.

"The police as well as my men have been busy with their range finders, but to no effect. It has been definitely established the crook moves around fast to avoid being caught, and evidently carries a powerful transmitter and receiving set with him."

"I'll bet if the carrier wave were traced to its sending point, the radio itself would be cleverly hidden-inside an animal or another place no one would suspect," guessed Joe,

"I'm afraid so," his father answered. "But let's talk of another matter for a moment. I had your mother on the phone--"

"How is she?" the boys chorused eagerly.

"Feeling very well. She'll be home soon. I expect her before you leave."

"Leave?" asked Frank, puzzled. "Where are we going?"

"Have you forgotten about the plane trip with Professor Wood to look for the lost scientists?" Mr. Hardy smiled. "Of course, if you don't want to go--"

"Oh, we do!" cried Joe.

"Well, your mother says she'll give her permission if the professor is with you and if the plane has a reliable pilot."

The boys were highly excited. Just where the hunt for the missing men would take them they did not know. But it promised travel and real adventure. They only hoped the lost scientists would be found alive.

"I've decided to have you take the new walkie-talkie with you on the trip," said Mr. Hardy to Ms sons.

"So we can keep in touch with you, Dad!" Frank wanted to know.

"Partly that, yes. I have obtained permission for you to contact the Royal Mounted Police by short-wave radio in an emergency. American amateurs are permitted to operate in Canada if they notify the authorities beforehand. If you are searching on foot, the walkie-talkie will keep you in touch with the outside world."

"You certainly make the trip sound intriguing," remarked Frank, his eyes shining in anticipation.

"Let's go tell Chet!" whooped Joe.

The boys found their stout chum vainly trying to stretch the pelt of the deer over a wooden frame, or manikin, he had made. This was to be Chet's major achievement as a taxidermist. But he was making wretched progress, for the deerskin fitted in very few places.

When they told him about the coming airplane flight in search of the lost scientists, to their surprise, Chet was not envious.

"You can have it," he said. " I'll stay on the ground, right here in good old Bayport where I'm safe. That is," he added hastily as he remembered the kidnaper's warning note on the door, "as long as kidnapers leave me alone. Gee whiz, I hope your father catches those fellows pretty soon."

"I do too," said Frank. "I hate to give up helping Dad on the mystery. And it doesn't look as if it were going to be solved before we leave."

"Don't worry. I'll handle it for you," volunteered Chet, throwing out his chest. "I'll probably have it all cleared up by the time you get back." He wrestled with the deerskin a while and then sat down on a bench. "I give up," he said. "Either the manikin is too big or the deerskin is too small. I can't figure out which."

"Better make a new frame," advised Frank.

Suddenly Chet looked up. "Oh, yes-I just remembered. Bring back an otter for me, if you see one. I was in Roundtree's store this morning and he said nobody has ever mounted an otter correctly. Everybody mounts them as If they walk straight, and really they walk with a hunched back. So bring me one, will you, and I'11 fix it right."

The Hardy boys smiled. At the rate their friend was going, it was doubtful if he ever would finish anything.

"We don't even know yet where we 're going," said Frank.

"Well, if you get to Canada, or any other place where they have otters, see if you can catch one." Chet frowned. "Seems to me I had a message for you fellows but I can't recall it now."

"From Mr. Roundtree?"

"Oh, yes, I know. He said to tell you the fellow who bought the stuffed wolf from him just bought two stuffed foxes."

Frank whistled. " I think we 'd better go right down and have a talk with Mr. Roundtree, Joe."

At that moment the boys heard footsteps on the stairs to the taxidermy shop.

"Here's the place, Ma," chirped a voice which proved to be Jimmy Gordon's. "You'll like it."

The youngster had brought his mother to visit the studio. The Hardys were amazed at her somber clothes and friendly smile. Puffing a little from her climb up the stairs, Mrs. Gordon, looked around her curiously. Gallantly, the brothers went forward to welcome her. Chet dragged out a chair and dusted it off quickly.

"This is certainly a grand surprise, Mrs. Gordon," Joe said, wondering why the woman had come.

"What do you think of it, Ma?" asked Jimmy eagerly. "Isn't it swell? You'11 let me come here to help the fellows when I can, won't you?"

"It's a wonderful place for you, Jimmy," replied Mrs. Gordon. " And now suppose you wait downstairs while I talk to your friends." After he had gone, she turned to the Hardy boys. "The reason I came here," she said quietly, "was to thank you for what you've done for my son. I'm afraid I didn't understand at first. I thought he might be getting into bad company- again."

"Again?" asked Frank.

"Oh, I don't mean his mischievous young friends. Jimmy has a great capacity for hero-worship, as you may have noticed," she explained. "There was a time when to him my brother-in-law was the finest man in the world!. But Elly Batter set a bad example. He talked too much about easy money. Mr. Gordon and I were away from home a lot, so Jimmy saw a good deal of his uncle-too much for his own good.

"If you boys hadn't taken an interest in my boy just when you did, there's no telling where he might have wound up. Since my husband has been home, he and I have had a chance to talk things over, and we've decided to be with Jimmy as much as possible after this."

The Hardys were pleased. Life would be happy for the youngster from now on, they knew. They showed Mrs. Gordon around the taxidermy studio and Chet proudly exhibited the manikin, which Jimmy had helped to build. When his mother left, it was with the assurance that the lad would come to the Hardy place as often as he wished.

"But don't let him become a nuisance," the woman warned them with a smile. "He's extremely fond of you boys."

"Jimmy couldn't be a nuisance if he tried," the three youths assured Mrs. Gordon.

At the door she hesitated a moment as if she decided to speak about something else. Finally she said: "If Elly Batter has been up to any wrongdoing, I hope he'll be punished for it. And I want you to know that Jimmy's father hasn't any more use for Elly than I have."

The brothers were relieved to hear this. Any embarrassment they might have felt in having Elly Batter apprehended need worry them B.Q longer.

As Mrs. Gordon went down the steps, Jimmy came up. He perched himself on a table and said mysteriously:

"I've got information."

"About Mr. Zetter?"

The boy nodded. "There's a stuffed fox in his cellar. There were two, but he wrapped the other one up and mailed it. I saw the address. He sent it to a man named Andrew Smith. I wonder if that's my uncle's friend."

"Did he send it to Old Creek?" asked Frank eagerly.

Jimmy shook his head. "Nope. The address was Bloomington. I know, because I read it twice. It was Bloomington." The lad slipped down from the table. "So long. I've got to catch up to Ma. Then I'm going back to Zetter's to mind the store."

The boy scampered off downstairs, little realizing how important his information had been. Here was a direct clue, not only linking the mysterious Andrew Smith with Zetter, the electrical dealer, but pointing directly to Smith's present whereabouts.

There was a hasty conference. The first impulse of the Hardy boys was to go directly to Bloomington in the hope of tracking down Andrew Smith. But it seemed to Frank that Zetter would bear immediate investigation as well, so they agreed to divide forces. Frank and Chet would go to Bloomington, leaving Joe to check up on the electrical store.

Chet was not too excited over the prospect of another adventure, especially since there was a likelihood of his running up against lawbreakers. But Frank pointed out that if the stout boy were going to solve the mystery while they were away with Professor Wood, he had better get some practice. So Chet was forced to go to Bloomington after all. He climbed into the roadster with Frank and Joe, and the car sped off down the street. Joe was dropped at Zetter's store, where he found Jimmy alone in the shop.

"Mr. Zetter had to go out," the lad said. "He won't be back for half an hour. Do you want to look at the fox in the cellar?"

"Sure. And let's hurry.*'

Jimmy led the way down the stairs. At the bottom he switched on the electric light-one small, dim bulb that glowed eerily through the dusty gloom.

"The fox is right at the far end of the cellar," whispered Jimmy. "You can't see it from here." He led the way across the rough floor.

Suddenly there was a loud bang. Joe wheeled, flinging a startled glance over his shoulder. The trap door at the top of the cellar stairs had been slammed shut. Zetter must have come back sooner than he had said he would.'

In the same moment the light went out, and the cellar was plunged into complete darkness, Then came a startled shriek from Jimmy.

"Joe! "he yelled. "Help!"

The Hardy boy heard a dull thud. After that there was utter silence.

"Jimmy!" he cried in alarm. " Jimmy I"

There was no answer.

CHAPTER XIX

THE ILLEGAL FACTORY

FORTUNATELY, Joe had a flashlight in his hip pocket. It had served him well in the past and he seldom went on any mission without it.

In the beam of light he caught sight of a dark gap in the floor ahead. When he came closer to the opening, he saw a trap door swinging from its hinges at the brink. He turned the rays of the flashlight downward. There, in a small sub-cellar, Jimmy lay sprawled on the ground.

"Jimmy!" whispered Joe tensely, fearful of what might have happened to the lad.

Joe quickly swung himself over the side and dropped through the trap door. The subcellar was so low that he knew he could easily pull himself up through the opening again.

"Jimmy!"

As Joe flashed the light directly in the lad's eyes again, the youngster stirred and tried to sit up. He began to rub his head, and tears came into his eyes.

"You hurt?" Joe asked quickly.

"I 'm O.K.," the boy answered bravely. " Got the wind knocked out of me. And I guess I bumped my head when I fell." He looked up. "Where am I, Joe?" he asked, bewildered for the moment.

"In a subcellar under Zetter's shop. I'll boost you up through that trap door. But first of all, let's have a look around." Joe flashed his light about the place. Jimmy uttered a cry of surprise. " Gosh!" he exclaimed. " Radios! All kinds of'em!"

Stacked against the brick wall were at least fifty new and up-to-date sets. Quickly Joe ran his eye over them for a manufacturer's label. There was none. The boy's heart jumped with excitement, when he realized that maybe he had stumbled onto the key that would unlock the whole mystery I This might well prove to be the turning point in the Hardys' efforts to round up the Hudson gang.

"Come on. Jimmy," he said. "We must get out of here. Don't tell Mr. Zetter you saw the radios. I don't believe he 'd like it."

He hoisted the lad up through the opening, then hauled himself back into the main cellar. His flashlight now revealed the stuffed fox Jimmy had mentioned, standing against the back wall. Joe went over to the animal and picked it up. The fox was heavy, and the reason soon became apparent to him. A compact shortwave receiver and transmitter had been deftly packed inside.

"Jimmy, you must promise to say nothing about this to anyone," Joe cautioned.

"Gosh, no," the lad grinned. " It's got something to do with detective work, hasn't it! I won't breathe a word."

"Try the trap door, Jimmy."

The boy ran up the stairs and endeavored to raise it. But the door had not merely slammed shut. It had been locked.

"Can't budge the thing," panted Jimmy. "Do you want me to bang on it!"

"Never mind," replied Joe, who thought it might be just as well not to have Zetter see him. "Maybe we can find another way of getting out of here."

When he discovered the door to the alley locked from the outside, he was sure Zetter had locked them in on purpose and was planning a getaway. Quickly Joe crouched over the radio in the stuffed fox. In a few minutes he was speaking to Chief Collig. Five minutes later the most surprised man in all Bayport was Mr. Zetter, of Zetter's Electrical Repair Shop, when a police car pulled up in front of his place of business and two officers strode through his doorway just as he was hurrying out.

"All right, Zetter. Let those two boys out of the basement. And make it snappy."

"Boys!" exclaimed the shopkeeper. "I don't know what you're talking about."

"Open up that basement and stop arguing!" ordered one of the policemen.

Zetter professed to be astonished when Joe Hardy and Jimmy Gordon scrambled through the trap door. He professed to be even more astounded when the black market radios were carried out of the subbasement. But his loud declarations of innocence had no weight with the officers. Zetter was taken to Headquarters.

In the meantime Frank Hardy and Chet had arrived at the little village of Bloomington, where they had driven to the general store and post office in the hope of locating "Andrew Smith." The motherly old lady who ran the place was friendly.

"Andrew Smith?" she said thoughtfully. "No-there's nobody of that name in Bloomington. But wait a minute-seems to me a package marked for him came this morning."

She rummaged through some articles under the counter.

"That's right," she assured them. "It's addressed to Andrew Smith, Bloomington. Must be a newcomer to the village. Is he moving here to stay?"

"We don't know," said Frank. "But if there's a parcel here for him, he'll probably be along to claim it."

They went back to the roadster, where Frank outlined a plan of action.

"You had better hang around the store," he told Chet. " I'll stay in the car and watch everyone who drives by. Maybe Elly Batter will come along."

"You mean I'm to stand around in that store all day?" Chet protested.

"We may not have to wait long. If Elly Batter is expecting that parcel, he'll probably come for it soon. As for hanging around the store, why not do some shopping? I saw some chocolate bars in a showcase. And there were all kinds of crackers."

Chet brightened up and hastened back inside the shop. There he purchased, progressively, a handful of chocolate bars, a bottle of lemon soda, half a pound of fig crackers, three oranges, two ice cream cones and a small bottle of pickles. He ate all of these in the course of an hour.

At the end of that time the woman was regarding him with a good deal of amazement. She had never had a customer quite like Chet. And even Chet was beginning to feel uncomfortably full. For once in his life he had had enough to eat! Having reached the bursting point, the fat boy was looking at the shelves in the back of the store to see what else he could buy except food, when he heard the old lady say:

"Yes, there's a parcel for Mr. Smith. Here it is."

Chet turned in time to see a man take a package from the postal window near the door and dash outside.

"That wasn't your friend after all," the old lady said regretfully to the stout boy. "He sent someone for his mail. Maybe if you hurry, he'll tell you where to find Mr. Smith."

Chet already was hurrying. He was just in time to see the stranger jump into a car and drive away.

"There's your man," he puffed to Frank, scrambling in beside him.

The Hardy boy was puzzled. The fellow who had come from the store was not Elly Batter. An explanation from Chet as they followed the other car cleared that up; the mysterious "Andrew Smith" was too wary to call for his mail in person.

The stranger ahead turned into a lane leading to a farm half a mile out of Bloomington. The boys followed as close as they dared without risking detection. Then they parked the roadster and made their way toward the house on foot. The place was well sheltered by trees, so they were able to creep within sight of it without being seen.

The man who had picked up the parcel at the post office was standing on the farmhouse porch talking to another man. And that other man was Elly Batter! At last they had tracked the tall, thin crook to his hiding place!

As they watched, he went into the house with the package, and the other fellow came down the steps, got into his car, and drove off. Frank jotted down the license number.

"Keep an eye on the house," he said quietly to Chet. "I'm going to take a look around."

He circled through the underbrush toward the back of the building. The place was unkempt; weeds grew high in the yard and there were no crops in the field. At the rear was a two-story wagon house, apparently empty. But as Frank drew closer, he could hear sounds of activity coming from upstairs in the building.

At a quick glance the youth noted that the ground rose sharply toward the rear of the wagon house. Cautiously he crept up the slope and peered through one of the back windows,

At a long table sat a man working on a radio.

Near by were a dozen other sets in various stages of assembly. All about the room were parts and supplies, as well as rows of finished instruments. Some of them were crated, ready for shipment.

Frank took in all this at one astounded glance. Suddenly, as the fellow turned from the table to reach for a coil of fine wire, the boy got a good look at his face.

Zetter!

Frank could not believe his eyes. So the fellow was working in this secret radio factory and also operating a repair shop in Bayport!

"He makes the radios from stolen parts and sells them at his shop," thought Frank.

As the boy watched the man closely, he realized that this was not the Zetter of the Bayport store at all. This man was slightly older, yet he looked enough like the shopkeeper to be his twin.

So intent was Frank on the thought that he failed to hear a figure approaching the wagon house from the front. He was Batter. The man started up the incline toward the rear of the building.

The fellow at the work table inside evidently heard the sound of his approach, however. In an instant he whipped a revolver from his pocket and turned toward the window where Frank was standing. The boy dropped from sight just in time. He ran on tiptoe toward the side of the old structure, reaching the corner of it just before Batter did.

Frank was in a bad spot. Although he had glimpsed the oncoming figure without having been seen, the youth knew he could not get to the other side of the wagon house in time to escape detection. Even if he could, the fellow inside might look from the window al. any moment and spot him.

What was Frank to do?

In desperation he sought a hiding place. There was only one possibility; a two-foot square door which hung partly open from the side of the building might offer concealment. Frank decided to find out, hoping it was not an entrance into the room where the man with the gun was waiting.

Swiftly he yanked open the door, peered into a grain bin, and scrambled to safety just as Batter appeared around the corner of the building.

"Hey, Zeke!" the thief called.

"Oh, it's you, Billy," came a reply from the window. "What's up!"

"Just wanted to tell you everything's ready in Chicago," Batter said.

"About time," stated Zeke. "Things are<* gettin' too hot around here for comfort."

"I 'm goin' to eat my lunch now and then go, * * Batter called, as he started down the slope.

Frank waited in his cramped hiding place until he thought the man was back in the farm-house and Zeke had returned to work. Then cautiously the lad emerged and sped back to the place where he had left Chet. Quickly he reported to his chum what he had seen.

"Wait here," he instructed the fat boy. "I'm going to get the police."

Chet did not like the idea of being left alone. He turned slightly pale.

"B-but what if B-Batter c-comes out?" he said, his teeth chattering.

"Hold onto him. Don't let him get away. Whatever you do, don't let that crook escape!"

Frank sped off down the lane. A few minutes later the quaking Chet heard the sound of the roadster as Frank turned it in the road and hurried back to Bloomington.

Five minutes passed. Ten minutes. Fifteen. The stout lad, crouching near a hedge, began to relax. Finally he decided there was no cause for alarm. Elly Batter probably would stay around the farm all day. In the meantime Frank would come with dozens of big, husky policemen.

Just then the door of the house opened. Elly Batter stepped onto the porch. He was wearing a hat and carrying a valise.

Chet groaned. Gulping, he crawled through the hedge. His knees knocked together as he went out to face Elly Batter!

CHAPTER XX

A CLUE TO HTJDSOH

FRANK had not wasted time trying to find Bloomington's village constable. He had telephoned from the general store to the State Police, and several troopers had sped by car to Bloomington in short order.

When they arrived, Frank led the way to Batter's farm. As he drove down the lane toward the house, with the officers close behind, he found Chet obeying his instructions to the letter.

The fat boy and Elly Batter were rolling in the dust, locked in struggle. Just as the police reached the yard the thief pulled himself free and scrambled to his feet. He cast one look of alarm at the troopers, and headed straight for a fence.

But the police were too quick for him. A fleet-footed officer overhauled Batter as he was about to jump over and grabbed him. There was a gleam of steel as handcuffs snapped on the culprit's wrists.

"Gosh!" panted Chet, crawling to his feet. *' You got here just in time. I was about winded." He was puffing from his exertions as well as the large quantity of food he had eaten at the village store.

"You did a swell job," Frank praised him. "How'd you manage to hold Batter!"

"First I told him I wanted the ten dollars he'd cheated me out of over the dead deer," explained Chet. "We argued a long while about that, but he gave it to me finally!" the boy said proudly. "He thought he'd got rid of me, but when he started to walk away I grabbed him. Gee whiz, what a fight!" Tenderly, Chet touched his left eye, which was swelling rapidly and turning black.

In the meantime the police had quickly searched the house and the outbuildings. The man who looked like Zetter was brought from the wagon house, protesting his innocence of any wrong-doing in connection with the radio work. But one of the troopers, who happened to be a radio expert, pointed out a certain red-covered wire in one of the radios. " Clever little way you had of attaching this," he said. "All the black market radios we 'vet uncovered around here had the job done this way."

"Here's some more evidence," announced another policeman. "Stolen parts from the Acme Electronics Company."

"That settles it," said a third, who was the trooper in charge of the group. "You two men are under arrest for possessing stolen goods and running an illegal radio factory."

Batter was sullen. "This ain't our place!" he cried out. "Zetter and I are only hired to work here. If it's stolen stuff, we don't know anything about it."

"Where's Spike Hudson?" demanded Frank suddenly, taking a flier on getting some information from the crook.

"Never heard of him."

Frank produced the note he and Joe had found on the road not far from the abandoned secret factory along Willow River-the note addressed to Andrew Smith and signed with the initials S. H.

"How about this? We know you use the name Smith. And those are the initials of your boss Spike Hudson."

Batter's attitude changed suddenly. His eyes gleamed at Frank Hardy with a consuming hatred. "All right. You got me cold. But one thing you got wrong. Hudson's not my boss," he snarled. "I'm the brains of the whole outfit. Spike and his boys only work when I give the orders!"

"I suppose you're the clever one who thought up all those short-wave radio signals including 'Help-Hudson,' " suggested Frank.

Elly Batter looked puzzled. " We used shortwave to get messages to each other," he admitted, "but 'Help-Hudson' wasn't one of them."

"Where's Spike now?" asked Frank, wondering if the racketeer used the signal for some other purpose.

"That's for you to find out," sneered Batter. "I won't squeal on him. You'll never find him through me."

Although Frank and the police continued to question the two prisoners, they resolutely refused to give any further information. Finally the troopers thrust the men into the squad ear and drove off with them. Frank and Chet followed in the roadster.

"Well," declared Chet, beginning to be proud of his black eye, "that's what I'd call a good day's work. Another mystery solved."

"It won't be solved until we round up the whole Hudson gang," declared Frank.

When the boys returned to the Hardy home they found the household in an excited state. Joe had just come in with a report of the arrest of Zetter, the electrical repair shop owner. Chet's eyes bulged.

"Gee, things sure are moving," he said.

Aunt Gertrude was in a state of nervous agitation because Fenton Hardy, who had left home directly after luncheon by plane, had been trying to reach his sons by telephone from a hotel in a mid-western city.

"You 're to get in touch with the long distance operator right away," she said. "And what's more, Professor Wood called here a little while ago. He said he would be back. He's arranging for the airplane trip to hunt for his friends. And Chet Morton, you 've got to have a poultice on that eye. Come with me!"

As the stout boy was hustled away, Frank called the long distance operator. In a few minutes he heard his father's voice.

"I didn't want to worry your Aunt Gertrude," began Mr. Hardy. "That's why I asked to speak to you. I had a little accident- - sprained my ankle-and I'll be laid up here for a couple of days."

"We'll carry on here, Dad, and give tip our trip with the Professor."

"No, I don't want you to do that. I think a vacation will be good for you, and you can be very helpful to Professor Wood. Anyway, I've had a little luck on the Hudson case, Frank- I rounded up two of the men I wanted, although I haven't located Hudson himself yet."

"We've had some luck too," said Frank.

He told his father about the arrest of Elly Batter and the two Zetter brothers. When he related how Batter had claimed to be the brains of the gang, Fenton Hardy laughed skeptically.

"The man's just bragging," he said. "He's known as a cheap crook, but he probably got hold of a little money and made an impression on Spike."

"You mean he swindled a lot of people like he did Chet?"

"Yes, only for larger sums, probably. Hudson is the head of the radio racket. He's a slick, cruel gangster and Batter is just a henchman of Ms."

Frank mentioned the fact that Batter had admitted the gang used signals on short-wave transmitters, but that "Help-Hudson" was not one of them. Mr. Hardy disagreed with his son's theory that Spike might be using it for another purpose. **

"In that case wouldn't transmit that message on the same frequency as the other signals," the detective objected. "No, it's more likely someone else has been sending out those words."

"But what could they mean?"

"I have no idea. Well, forget the whole thing for a while and enjoy yourselves on the trip. I hope you locate those scientists unharmed."

Frank was just turning away from the telephone when Professor Wood rang the doorbell. The elderly man was agog with news about the impending search.

"We haven't had any word from the missing party," he told the Hardys, "but from various reports we think they've probably been forced down by a storm somewhere in Canada."

"Canada! Is that where we're going?" exclaimed Joe.

"I think so. We'll probably have the destination better settled by tomorrow and I hope to leave early the following day. In the meantime I'd like to have your luggage tomorrow so it can be weighed and put in the plane. I'll come around for it in the morning."

"We'll have everything ready," said Frank.

The scientist hurried away, for he had a great many arrangements to make. Frank and Joe, highly excited, began making a list of the items they would take with them. In this they were assisted by Aunt Gertrude, whose suggestions were mainly concerned with navy underwear, plenty of warm socks and a set handkerchiefs. The boys themselves loaded up with the new walkie-talkie set and wondered whether their skis would be helpful.

"All depends on what part of Canada we go to," said Frank. "If it's the far north we'll probably find snow at this time of year. We'd better put them in."

The next morning found them busy packing, They kept their luggage as compact as possible, and when Professor Wood called for it in a taxi at ten o 'clock he complimented them on the restraint they had shown.

"I'm sure the pilot will have no complaint about this amount," he smiled. " He was afraid you would want to bring enough stuff for a round-the-world jaunt. And by the way, if you'll come out to the airport about noon he would like to see you. His copilot hasn't shown tip yet and he wonders if you know anything about flying."

The brothers smiled and admitted that they did.

"Then go out and get acquainted with the plane," said the professor.

"We'll be there," promised Joe.

He and Frank carried the bags out to the taxi in a state of high excitement. The trip was opening endless possibilities. They found themselves hoping the copilot would not show up!

When they went out to the garage loft to see Chet, they discovered their chum was in a gloomy mood Taxidermy had lost its appeal for him.

"I'm beginning to think I'll never get this deer finished," he sighed. "It just keeps getting fat and bulgy, and always in the wrong places. It looks more like a cow than a deer."

"Cheer up!" laughed Joe. " We 're going to Canada and we'll try to get an otter for you."

"Honest!" Chet beamed, but only for a moment. As he realized his chums were going to be away, he began to feel lonesome.

The unannounced arrival of Jimmy Gordon created a diversion for him, however. The youngster had brought a couple of gifts, crudely wrapped in crumpled tissue paper.

"I kinda thought these might come in useful on your trip," he said hesitantly to the Hardys. "In case you had to cut firewood or something. I bought 'em out of my earnings."

Jimmy bad purchased small pocketknives for Frank and Joe. They were touched. The knives were of inexpensive quality and not likely to be useful for any task heavier than sharpening pencils. But the brothers assured Jimmy that his gifts were exactly what they needed to complete their equipment. The lad's face shone with pleasure.

"You really like 'em?" he asked. "Gosh- I hardly knew what to get, but I wanted to give you something. Then all of a sudden it came to me. Chet said you might be going to Canada. 'Hunting knives,' I said to myself. 'That's what they'll need.' I'm certainly glad you like 'em."

"While we're away, Jimmy, I want you to keep an eye on Mickey. See that he behaves himself, will you?" Frank asked him.

"Don't you worry about Mickey. He's coming here today. And I'll keep on helping Chet with the taxidermy too, now that Zetter 's in jail. Maybe we'll even get that deer finished before you come back!" But Jimmy's glance at the somewhat lopsided and corpulent specimen was a shade doubtful. "That is, if you're away a couple of months, maybe."

"Heard anything from your Uncle Elly?" asked Frank carelessly. He wondered if Jimmy had learned that the man was in jail.

Jimmy shook his head. "We heard he went to visit his rich friend," said the boy.

"Rich friend?"

"Oh, he used to tell me about a friend of his who lives in a big house. Sort of a funny man. He put all kinds of stuffed animals around his grounds to frighten people away."

The Hardy boys looked at each other. Had Jimmy unwittingly dropped a valuable clue? Could the place be one of Spike Hudson's hide-outs?

CEAPTEB XXI

A STRANGE GARDEN

Tell us all you can remember about the house your uncle's rich, friend owns," Frank asked Jimmy Gordon.

The lad wrinkled Ms forehead and looked off into space a few moments. At last he spoke.

"Uncle Elly never told me about the inside of the house, but if he ever comes around to see us again, I'll ask him and tell you."

"That won't be necessary," Frank spoke up quickly. "We were sort of interested when you said the man put stuffed animals around his grounds to scare away people."

"Maybe my uncle was only teasing me," said Jimmy. "I don't know who would be afraid of a stuffed animal. I wouldn't," he boasted.

Joe decided to prod the boy's memory, so he made the remark that the animals no doubt were placed among the trees. He laughingly suggested that the trees might be fakes, too.

"Oh, no," spoke up Jimmy Gordon quickly. "There's a real woods around the house. It's a swell place. Real big, and it even has a pond on it."

"A pond?" Joe repeated.

"Sure. A big one."

"Sounds like a good place to swim," remarked Frank. "You haven't any idea where it is, have you, Jimmy?"

"Nope. My uncle didn't tell me, except it ain't awful far from here."

The Hardys thanked Jimmy again for the knives he had brought them, and went to the house to hold a conference. The brothers were convinced that no time should be lost in trying to find the place with the stuffed animals.

"But where will we start?" sighed Joe. " There must be hundreds of houses around here with ponds on the grounds. And the place we want to find may not even be in this vicinity."

Frank was not to be talked out of trying to locate the building. Suddenly he snapped his fingers, saying he had a solution.

"We're to go up in the airplane this noon with Pilot Stewart, remember? It will give us a chance to look for a large house with a pond and a woods."

"A swell idea," agreed Joe.

He and Frank arrived at the airfield a half hour before the appointed time. The plane was being warmed up. The affable young aviator in charge of it said he was ready to instruct the Hardys in its workings.

"Pretty neat!" exclaimed Frank, as he climbed into the sleek-looking craft.

The boys took turns at the controls, practicing take-offs and landings. Pilot Stewart was amazed at their prowess and complimented them highly. When the lesson came to an end.

Frank asked Stewart if lie would do them a little favor.

"We are trying to locate a place where we think a crook is in hiding," he said. "If you could give us a few extra minutes, we'd like to look over this territory from the air."

Their instructor was very obliging, and took them for a half-hour trip in an ever-widening circle around Bayport. The brothers were about ready to admit defeat in their hope of locating a large house surrounded by woods, with a pond near by, when suddenly Frank pointed to a spot below them.

"There's one!" he cried out. "It certainly fits the description of the place we're looking for. The pond is shaped like a clover leaf."

Stewart banked the plane and went low over the treetops. The boys got a very good look at the building and grounds-so good, in fact, that when they appeared at a Bayport real estate dealer's office at four o 'clock, the man was able to identify the property at once from their description of it.

"There's only one spot around here that has a pond shaped like a clover leaf," the realtor said. "I understand it was bought by some out-of-town people. From Chicago, I think. I don't know much about the sale, but I 've heard folks say the new owners keep very much to themselves."

"You don't know the name of the man who bought it?" Frank asked.

"No, I never heard. The deal was handled from the Chicago end."

When the Hardy boys left the real estate office, Joe was eager to investigate the mysterious property at once. After talking it over, however, he agreed with Frank that they had better wait until it was nearly dark, since detection of their presence would be less likely at that time. Immediately after an early dinner they set out in their car and drove to the place.

"Got your flashlight, Joel" Frank inquired, as they hid the roadster in a secluded spot near a .hedge which surrounded the property.

"Yes, but we'd better not show a light until we have to."

"Eight. Let's crawl over the hedge here and go through the woods."

The boys talked in whispers. Through the trees they could see the outline of a large, un-lighted building.

"If this is Spike Hudson's place, I hope we don't meet him unexpectedly," said Frank.

The brothers worked their way toward the house cautiously. There was not a sound except the twittering of birds. Presently they came to the clover-leaf-shaped pond. Joe grabbed his brother's arm.

"Great Scott!" he whispered excitedly. "Look-just beyond that tree!"

"What is it?"

"A wolf!"

Not twenty feet away, staring balefully at them, and crouched in a rigid attitude as if ready to spring, was a great gray wolf. Its fangs were bared menacingly.

Frank felt a shiver of apprehension for a moment as the animal seemed to move. Then suddenly he laughed quietly.

"It's not alive," he announced. *' This beast's eyes don't shine in the dark."

Joe flicked his flashlight on the animal for a moment. "You're right," he said.

"Remember, Jimmy said there were stuffed animals on the place to scare visitors away," his brother reminded him.

"That one pretty nearly scared away this visitor," Joe admitted, relieved. " It's the nearest thing to a real wolf I've ever seen. But say, that just about proves we 're at the home of Elly Batter's rich friend. Say, I'll bet this wolf is the one the fellow hid in Zetter's cellar. It looks like it."

"Probably is. Wonder if there's a radio inside it." He examined the stuffed animal, but could find no evidence of a set.

The Hardys went on, making their way past the stuffed wolf. At the far corner of the pond a huge shape suddenly loomed up. Curious, the brothers advanced toward it.

"A plane!" whispered Frank.

Though the daylight was about gone, the boys could see that the aircraft was of a make several years old. Its wings were camouflaged by twigs and branches cut from near-by trees, making its detection from the air impossible. Not far away was an open field which obviously served for take-offs and landings.

As the Hardys stood examining the plane, the heavy silence was broken by a hideous uproar -first the deep-throated barking and baying of dogs, then ferocious snarls. The yelps were so blood-curdling and vicious that the boys shuddered. Had a pack of hounds been unleashed and set on their trail?

Frank and Joe moved like lightning toward the nearest trees, ready to climb up. But although the uproar of the dogs continued, it did not seem to come any nearer.

"I 've got a hunch," Frank said after they had waited several moments.

From his pocket he whipped out a tiny shortwave receiver his father had given him, and tuned it to the frequency they suspected Hudson used. The yelps and snarls of the dogs echoed from the set.

"Another signal!" said Joe tensely. " Something 's going to break!"

Frank remarked he was sure they were close to the actual source of the broadcast. Cautiously he and Joe stole toward the house, their hearts pounding wildly. Soon they were within a hundred feet of it.

Lights had been put on inside. Their rays revealed two bulky figures standing motionless on the lawn. One, much larger than the other, was that of a full-grown animal.

"A bear and a cub," whispered Joe, not frightened this time by the stuffed animals.

The Hardys went closer. Frank had an idea about the bear cub. It was exactly the size of the one that had disappeared so mysteriously from the taxidermy shop over their garage.

"In fact," he said quietly, after examining it, "I'd say it's Chet's stuffed bear cub!"

Two headlights suddenly flashed around a corner of the house, followed by the roar of a truck. The boys flung themselves flat on the grass in the shadow of the bears and waited. They had acted not a second too soon, for the headlights swung brilliantly across the lawn for an instant before the truck came to a stop in front of the house.

Its engine was left running, as a man jumped from the cab and disappeared inside the building. A few moments later he came out carrying an object of some kind in his arms. When he passed in front of the glaring headlights, the boys could see he was holding a stuffed fox. The man put it into the back of the truck, climbed into the cab, and drove off down the road.

"I think you'd better go back to our car,. Joe," said Frank quietly. "Get in touch with the police on the short-wave set and tell them as guardedly as you can about this place. In the meantime I'll prowl around and see what I can find out."

"Right," whispered Joe. "Take care of yourself. I shan't be long."

Silently as an Indian, he crept off into the shadows. Frank continued to study the house carefully for a while. Then he moved toward it, keeping to the shelter of the trees. He had an open space to negotiate on the roadway, so he waited until he thought it was safe, then sped swiftly across into the shadow of the building.

Hearing footsteps on the gravel path, Frank flattened himself against the side of the house within a thick cluster of vines. A moment later he became aware of a light flashing jerkily as a man approached. Its beam hovered dangerously close to the vines for a moment, but swung away again. The crunching footsteps grew fainter as the figure disappeared around the corner.

The Hardy boy crept along the side of the house. Presently he heard voices coming from an open window. Frank stole closer until he was directly beneath it.

"-if we pull off this job, we'll be on easy street," someone said in heavy tones. "I don't want anything to go wrong with it, though."

"We'll be careful, Spike."

"But if anything does go wrong, I want all these papers destroyed. Get that? I want 'em burned, if I 'm not here to burn 'em myself."

"O.K. But there won't be nothin' to go wrong."

"I dunno. Things have been too quiet tonight. And we haven't heard from the others. Now don't forget what I said about burning those papers. There's enough evidence in that bundle to send us all to the pen for years."

The voices faded away. The men evidently had gone into another room.

Frank was trembling with excitement. There was no doubt in his mind now. This was Spike Hudson's hide-out!

In the meantime Joe was hurrying back toward their car. He passed the place where the stuffed wolf stood. The hedge was not far ahead.

Suddenly the earth gave way beneath the boy's feet. He stumbled. There was a bright flash, a crackle of electricity, and he felt a violent shock-so violent, that it knocked him to the ground.

Joe's brain seemed to explode in violent patterns of blinding lights. He sprawled on the grass, unconscious.,

CHAPTEE XXII

CAPTURED

FRANK waited nearly half an hour for Joe to return. At last he decided to enter the house alone and gather what evidence he could find.

The window of the room in which Spike Hudson and his henchman had been talking was at least ten feet from the ground. But it was open. Frank tested the strength of the vines that grew along the side of the building. They were strong and tough. Carefully the boy began to pull himself up toward the window ledge.

The leaves rustled noisily. He waited, and when nothing happened, inched himself up farther. A quick movement, and he grabbed the ledge with his hands, pulled himself up, and looked in. Frank knew he was taking a desperate chance of being detected. What if only one of the men had left the room? But the boy saw no one, so he slid across the sill and swung him-' self to the floor.

Frank remembered Spike Hudson's remarks about certain evidence that was to be destroyed in case of trouble. By the dim light from a lamp in the hallway, he began a hasty search of the room. The most likely place for the evidence to be hidden would be in the drawers of a desk in the corner, he decided. But they proved to be empty.

Perhaps Hudson had taken the papers with him. Yet this did not seem likely. From the conversation he had overheard, Frank gathered that the crook had been showing someone where they were located, so that they might be found easily and destroyed, if necessary.

On a side table he saw a shadowy object that seemed somehow familiar. Frank approached it. A stuffed fox! Recalling the one at the factory with the concealed radio in it, he quickly searched for the hidden catch that might open the animal's side. At first he could not find it, and had almost decided this was not a trick fox, when his fingers located the metal snap. One of the animal's legs moved under his hands.

Inside the fox was a small bundle of papers, which Frank removed hastily. His first impulse was to put the documents in his pocket. But if one of the gang should catch him as he left the house, he would find the papers on him.

"I'll try something else," he concluded.

Swiftly he bent down and removed his shoes, divided the sheaf of papers into two piles, and thrust one inside each shoe. As he was tying up the laces, he heard a voice in a near-by room.

"Calling car seventeen-report to Headquarters-Report to Headquarters."

The Bayport police giving orders by shortwave! In a moment came music, then another program.

Frank tiptoed to the hall and looked out cautiously. A light shining through an open doorway opposite him revealed a thick-set, power-

fully built man seated at a table in front of a radio. He was tuning it from, one short-wave frequency to another.

Spike Hudson!

Frank had Jo difficulty in recognizing the man. He looked just like the police photograph Mr. Hardy had of him. The boy shivered involuntarily. At last he was practically face to face with one of the most widely hunted of criminals! .

A disturbing thought struck the youth. Hudson had picked up a police call. At any moment he might pick up Joe's message to the troopers! Disguised though it might be, Spike could interpret the words as trouble for himself and skip out before he could be captured!

"It wouldn't do much good for me to tackle that hulk of a man alone," Frank thought ruefully. "I'd sure lose the fight!"

If only he could disconnect the radio wires! But this was out of the question. Presently he reflected that luck might be with his brother and himself after all. Joe perhaps had flashed his message through before Hudson turned on the short-wave set.

Frank tiptoed backward through the room and went to the window through which he had entered. Looking out, he noticed a shadowy figure coming cautiously toward the house. Frank knew that walk. He sighed in relief. Here was Joe at last. Together they might be able to hold Hudson until the police could arrive.

Frank swung himself over the window sill and dropped to the ground. There he -whistled softly to attract his brother's attention.

"Joe!" he called softly. "Over here!"

The shadowy figure moved toward him, advancing across the driveway. The gravel crunched beneath his feet.

"Quiet, Joe!" Frank warned him. "Did you call the police?"

At the word "police" the dark shape suddenly crouched and sprang straight at him. Too late, Frank realized his mistake.

This was not Joe!

The Hardy boy ducked and dodged to one side. But the man grabbed him and swung him around, at the same time calling to someone else. Another man ran from the side of the house and headed toward them.

Frank struggled and almost got away, but the second fellow seized him by the collar. Against the two the youth was helpless. His arms were pinioned, and a light was flashed into his face. He blinked in the dazzling glare.

"So!" grunted one of the captors. "Looks like we've caught a spy."

"We'd better take him inside and turn him over to Spike," said the other.

They hustled Frank into the house. There he was taken to the room where he had seen Hudson listening to the short-wave radio. The chief of the gang looked up, frowning.

"We caught this guy outside the house under one of the windows, Spike."

Hudson studied Frank through narrowed eye-lids. For a while he did not speak. Then he snapped:

"All right-start talking! Who sent you here?"

Frank tried to put up a bluff. " You 'd better take it easy, Hudson," he said. "The game is up for you fellows. The police are wise to you."

The crook glanced at his two henchmen., " Everything quiet outside? No cars around?" he asked.

"Everything as usual, Spike."

Hudson looked at Frank. "Just bluffing, huh? You'd better talk, boy. What brings you prowling around here I"

"The radio racket," said Frank calmly.

This shot went home. One of the men muttered, "Maybe this ain't no bluff after all." The other said, "Call up Batter on the phone and see if he knows what's going on."

"You'll have to ask the police first if you can talk to him," said Frank. " The Zetter brothers are in jail with him."

Spike Hudson rose swiftly to his feet. "Search this guy and lock him up in the little room," he ordered. " Gag and tie him. I guess things are getting too hot around here."

It was evident that the news of the arrest of Elly Batter and the Zetter brothers had been something of a bombshell. Hudson's henchmen grabbed Frank. He was tied hand and foot, and a gag was bound across his mouth. Then he was carried to a small, windowless room in the lower part of the house. Hudson came hurrying down the hall just as the two men were about to close the door. He snarled at the Hardy boy:

"All men ain't so kind as me. Some of 'em in my position would put you out of the way for keeps. Me, I don't hurt nobody unless I have to. I just make it mighty uncomfortable for any guy who gets in my way." He grinned cruelly. "By the time you get out of here-if you ever do get out-I'll be a long way from this place." Then he turned to the two men. "Did you search him?"

The men turned Prank's pockets inside out, but they did not look in his shoes. Frank was fearful that Hudson might think of it, and thus the papers he had removed from the fox would be discovered.

"Nothin' here," the men reported.

"O.K. Get busy and destroy all the evidence that's around. Break those animal sound records. Smash 'em all up."

The door to Frank's prison slammed shut The youth, lying bound and helpless on the cement floor, heard Hudson and his men ransacking the house. First came the cracking sounds of demolished records, then the odor of burning wood. Once he heard Hudson say to a man as lie went past the door:

"How about the papers in the fox?"

"Hooked. They're gone. Shorty must have burned 'em."

Their footsteps became fainter down the hall-Way. Then a door slammed in the distance.

A little later Frank heard the sputter of an airplane engine. It rose to a high, whining roar.

"Hudson has escaped!" Frank thought, furious that he had been partly to blame for the escape.

He struggled to free himself from the ropes and the gag. Up to the moment he had heard the plane's motor, he had held out hope that Joe might have warned the police in time to block Hudson's flight. The roar of the engine soon became a distant drone, and the boy knew the criminal had gotten away.

A door slammed again. Once more Frank heard footsteps in the hall, then the voice of one of the men who had captured him.

"Spike's too smart to take us with him. He 'a left us here to take the rap."

"Where did he go?"

"He's got a hide-out up in Canada. I don't know where it is, but he said he took his name from it, Hudson ain't his real name, you know. I figure he's gone up there. He'll be back when things cool off here."

"Yeah-and in the meantime we're supposed to stick around and wait for the cops to grab us. Why should Spike get all the breaks! I'm for gettin' out of this place, and pronto."

"Now you're talking sense. How about the boy?"

"Leave him where he is."

"Yes, but he'll starve to death if nobody comes here."

"Who cares? He got into this jam by himself. Let him get out by himself. If we let him go, you know what'11 happen to us, don't you? Let's take the ear and start travelin' while we've got a head start."

Their voices died away. In a few minutes Frank heard an automobile speeding off down the driveway,

CHAPTER XXIII

IN THE FAR NORTH

DAWN was beginning to show in the eastern sky when Joe Hardy finally regained consciousness. He found himself lying in the wet grass, and for a moment he could not recall what had happened. But as the mist cleared from his mind, he began to remember things. Slowly the boy got to his feet and stumbled back groggily toward Spike Hudson's house.

Joe knew he had been unconscious for hours. What was the devilish contraption that had knocked him out? Probably a trap-just the kind of thing a crook would use.

"Why hadn't Frank come in search of him? A horrible thought struck Joe. Maybe his brother had met the same fate! But as he came in sight of the house, Joe recalled that Frank was supposed to stay there to find out what he could, so probably he was all right.

To the boy's surprise the place apparently was deserted and unguarded. The front door stood wide open and the airplane was gone.

"It might be a trap," the youth thought suspiciously. "I'd better watch my step going inside."

He waited near a big tree, watching. Then he decided on a course of action and walked boldly across the grass. If anyone should challenge him, he would pretend he had lost his way and had wandered onto the grounds by mistake.

There was no sound from the house as the Hardy boy walked up the steps. He rang the bell, which echoed hollowly through the building. No one came to answer it.

Joe went inside. From the evidence of confusion that he found-scattered papers and overturned furniture-he gathered that the occupants had fled in haste.

But where was Frank? Had they captured him and taken him along?

Joe searched the house upstairs and down, yanking open doors to rooms and closets. But nothing came to light until he reached the basement. Here he found one door locked. As the boy tried to open it, he heard a strangled sound from inside the room.

Could it be Frank?

Joe flung himself against the door. It would not give. Seeing an axe in a corner, he grabbed it up and smashed the heavy wood. Splinters flew. The catch shattered. Joe kicked the door open.

"Frank!" he cried in relief.

In an instant he had untied the gag across his brother's mouth. Swift slashes of his jack-knife cut the ropes.

Frank, stiff and cramped from his all-night imprisonment, related to Joe what had happened. He also revealed that Spike Hudson had escaped by airplane for a hide-out in Canada, and told how he had heard the crook had taken the name of the place for his own.

"I'll bet it's Hudson Bay!" he concluded.

Joe became excited. "Wait a minute!" he cried. "I saw a paper--"

Dashing to the room which evidently had been used as an office, the boy looked at several torn pieces of paper scattered on the floor. In a moment he picked up one of them and hurried back to Frank,

"Here's part of a map," he said. "It may or may not mean anything, but there's a penciled line on it running from Buffalo right up the east coast of Hudson Bay."

Frank peered at the map. "The line ends at a place called White Bear River," he said.

"Don't you think we ought to report this to the police?" asked Joe.

"Police?" exclaimed his brother impatiently. "Why ask them to look? We're only guessing where he went, after all. Why can't we trail Spike Hudson?"

Joe's eyes bulged. " How can we?"

"In Professor Wood's plane!"

"Say, that's a great idea," agreed Joe, "but do you really think we ought to ask the professor to start off on a hunt for Spike Hudson? After all, he hired the plane to look for his lost friends."

"I had plenty of time to figure things out last night," Frank replied. "I have a new idea about the 'Help-Hudson' signal. We took it for granted that it had some connection with Spike Hudson, but you recall Billy Batter said he didn't use those words and Dad thought he didn't, either. Well, Professor "Wood believes his friends were forced down in some part of Canada. Maybe 'Help-Hudson' was part of a message sent over short-wave by the missing scientists!"

Joe gasped. The idea had logic. "You mean they're in the Hudson Bay country? If you're right, the professor certainly can't object to going there."

"We'd better hurry if we don't want to be left behind," his brother warned him. "Stew-art said he'd be taking off at eight o'clock and it's past that now."

The boys left the house and raced across the grounds. As they neared the spot where their roadster had been hidden, they began to wonder if it might have been stolen by some of Hudson's men. To their relief they found it still parked there.

Soon they were speeding toward the airport. Knowing Professor Wood was a stickler for punctuality, they became fearful that he might have left without them. But when the roadster swung through the entrance to the airport, they saw Stewart and the scientist supervising the activities of the mechanics who were preparing the plane for the flight.

"Well, I'm certainly relieved to see you," declared the professor as the boys ran up. "I telephoned your home but no one seemed to know where you were. You had better get in touch with your aunt right away. She's dreadfully worried."

"We'll phone her at once, sir. But in the meantime," said Frank, "we think we've hit on a clue that may be pretty important to you in your rescue work. Come over here while we tell you."

Out of earshot of the mechanics, the Hardys told the elderly man and the pilot about the flight of Spike, probably toward Hudson Bay, and of Frank's theory that the "Help-Hudson" messages might have come from the lost scientists. Professor Wood was deeply interested.

"Your reasoning is good," he complimented them. "You may be right about that signal. My friends had a short-wave transmitter with them." The scientist rubbed his chin thoughtfully. "But as for chasing this criminal-I'm not so sure. It might be dangerous."

"May as well kill two birds with one stone," spoke up Stewart. "I'll be glad to help all lean."

Being young, the thought of adventure appealed to him. Moreover, since meeting the Hardy boys he had inquired a little about them in Bayport. Learning of their many exploits, the pilot was rather keen to join them in tracking down a criminal.

"From what Frank says about the plane this Spike Hudson used, I doubt that it's very fast. Even if he has a few hours' head start. we may be able to catch him."

Professor Wood, seeing the eager looks on the three youthful faces before him, relented.

"Very well," he said with a smile. "We'll strike out for the Hudson Bay country. If my friends have been sending out calls for help, we can pick them up with clearer reception as we get closer to the spot. The sooner we get under way, the better, I suppose."

The pilot looked at the progress the mechanics were making. "We can take off in fifteen minutes, sir," he told the scientist.

"We'll make it thirty," decided Professor Wood. "I was young once," he said, his eyes twinkling. "And if there's one thing I remember about my youth more than anything else, it is that I used to forget to eat sometimes when I got excited about something, until all of a sudden I'd get so weak I--"

Frank and Joe grinned. "We could use a little time for breakfast," they said.

While the man at the lunch counter was preparing a meal for them worthy of Chet's capacity, the Hardys took turns making telephone calls. First they got in touch with their Aunt Gertrude to allay her fears. When she heard they were not coming home before leaving on the plane trip, she began one of her tirades.

"The very idea! Why, you can't get a bath at that airport. . Going off to Canada without one and wearing soiled clothes besides--"

"We have clean ones in our bags," Frank reminded her. But for the first time he gazed at himself and Joe critically. He had to admit they both looked pretty disheveled.

"I'm sure you haven't half enough warm clothing," Aunt Gertrude went on. "Up there in the frozen North you're likely to catch your death of cold, and besides--"

"Please don't worry," Frank interrupted her. Joe was pointing to a plate of bacon and eggs on the counter. "I really have to hurry now. Good-by, Aunty. Tell Mother when she comes we 're sorry not to have seen her."

He hung up, then called the long distance operator and asked her to connect him with Fenton Hardy at his mid-western hotel. While waiting for the connection, he ate some fruit and started on the bacon and eggs. Joe, having finished his meal, talked to his father when the call came through. The detective was amazed to hear the boy's report.

"Mighty fine work, son," he said. "I'll fly home to take a look at those papers Frank has in his shoes before turning them over to the authorities. Suppose you lock them up in the compartment of your roadster and ask Chet to come out there right away and take them and the car to our house."

He said also that he would report the whole affair to the authorities, including the Canadian police. He would ask them to stand by to give assistance in arresting Spike Hudson if the boys should locate him.

"All right, Dad," said Joe. "And take care of that ankle of yours."

"Don't worry, son, it's coming along all right," his father reassured him.

The boy next got in touch with Chet Morton, who was not yet out of bed. He teased the fat boy about not being on the job at the taxidermy shop. Before Chet could reply, Joe gave him instructions about the car.

"Well, gee whiz," said his chum, "I don't know. Some of those thieves--"

"I'll leave the key with the manager here," Joe interrupted. "We'll be halfway to the border before you're dressed!"

"Don't forget my otter!"

"O.K.," laughed Joe. "And get that deer finished, will you?"

Stewart came to see if the Hardys were ready. Frank and Joe hurried outside and climbed into the plane. The engines throbbed with life. The pilot sent his craft aloft and they soared off into the northern sky.

A stop was made at Buffalo, where the Hardys inquired if a plane answering the description of Spike Hudson's had landed there. From what they could learn, apparently it had not.

"We'll follow the route of that pencil line on the map you found," said Stewart, and headed the plane in that direction after they took off again.

Hours went by without the anxious travelers seeing a single plane. They kept the radio turned on the entire time, but heard nothing to help them. Once, however, the Hardys cried out in glee at a news announcement that came through: The well-known detective Fenton Hardy has apprehended several members of Spike Hudson's gang.

"Hurrah for Dad!" exclaimed Joe.

Some time later Stewart landed at a small airport on the outskirts of a northern Ontario town to see if he could pick up any information about Spike Hudson. From a forestry patrol official the party learned that a plane answering the description of the crook's aircraft had refuelled there about an hour before and had headed due north.

"We're right on his trail," Stewart assured the Hardy boys as they started off again. "At the speed we 're going now we should catch sight of him before long."

True to his prediction, they saw a speck in the sky a little later. Frank trained a pair of binoculars on it.

"Looks like Spike's!" he cried excitedly. "Give this bus all she's got, will you, Stewart?'-'

CHAPTER XXIV

A CALM FOG

PILOT STEWART sped through the sky after the fleeing crook, Spike Hudson.

"We're gaining!" cried Joe exuberantly. "It won't be long now!"

Suddenly the plane they were chasing seemed to shoot ahead. The Hardys thought Hudson had put on a burst of power, but Stewart knew such was not the case. Dolefully he looked at his gauges. Something was the matter with his own craft. He was losing speed, and everything he did to give the motors a spurt was of no avail. The expression on his face told the story, even before he mentioned the difficulty.

"I'm afraid we're going to lose that fellow," he said.

"You mean we'll have to go down!" asked Professor Wood, who had been consistently scanning the landscape below for a sign of his lost friends, while the others had been concentrating on Spike Hudson's plane.

"Not yet," Stewart replied. "I'll see what I can do. Frank, suppose you take over while I find out if some oil will remedy the trouble."

He was gone a few minutes. Upon his return he shrugged his shoulders. "Motors are getting hot," he reported. "I doubt that we can make White Bear River," lie added, exchanging places with Frank, "but we'll stay up as long as we can."

Although everything seemed to be all right for a while, the group became worried and conversation ceased. Joe had adjusted the earphones of the radio to his head. Tuning it to the wave length on which they had often heard strange messages, he suddenly cried out:

"I heard it! The signal!"

He switched the instrument quickly to the loudspeaker so the others might listen. Then, much stronger than the Hardy boys had ever been able to get it before, came the familiar call:

"Help-Hudson!" To it was added," White Bear--"

The voice died away for a moment. There was a splutter of static. Then:

"-notify Professor-crash-White Bear River--"

The signal became weaker. A roar of static drowned the distant voice.

"That's my party!" declared Professor Wood in excitement. "I'm sure of it. It sounded like Professor Henderson's voice!"

The group looked at one another in astonishment and not a little apprehension. Spike Hudson and the lost scientists all at White Bear River! It was possible the missing men had found the crook's isolated hide-out and were staying there, unable to leave. What would happen to them if Spike should show up?

The Hardys' worst fears were confirmed when they heard the signal again, very faint this time; but through the static they were able to distinguish certain figures-a degree of longitude that dovetailed exactly with the penciled line on the map Spike had left behind.

"I wish we dared speak to your friends on our transmitter, Professor "Wood," said Frank. "But it might warn Hudson we 're in the vicinity and he'd leave. Then we'd have no clue at all to his whereabouts."

Tense minutes went by as the big plane roared toward the destination indicated on the map. Once the starboard motor faltered and the pilot caught his breath, but it picked up again and they raced on.

Below them the land had grown white, for winter comes early to the Hudson Bay country. Snow lay on the frozen ground. Stewart nursed the engines along, but the boys and Professor Wood could see he was having trouble.

Suddenly one motor choked, then stalled. It would not start again. Immediately the pilot scanned the terrain below for a possible landing field. At the same moment the boys caught sight of a small river some distance ahead. Was it White Bear?

The plane droned through the sky, losing altitude. Presently Stewart banked it in a wide circle and descended toward a small lake, which was the only level spot on which to set down his ship. He hoped the snow-covered ice would be frozen deeply enough to support it.

"We've got to go down," he announced to the others. "The landing may be bumpy. I'd hoped to find a smoother field but this lake will have to do. Better adjust your safety belts."

Stewart circled the lake once, eyed it carefully, flew in low over the rocks on its shores, and set the craft down. There was a moment of suspense as the passengers waited to see if the ice would hold, as the plane bumped and jolted through the snow. But it rolled to a stop without sinking.

"That's that I "said Stewart grimly. " We 're lucky."

"I'll say we are," agreed Frank. "Only a fine pilot could have kept us from a crash."

"Too bad we couldn't make White Bear River," said Stewart. "But we'll get there somehow. And now how about you boys fixing something to eat while I take a look at the balky engine?"

Up to this time the travelers had had only cold food. Now the Hardys prepared a hot meal, while the professor listened intently to the short-wave radio. Not until sundown, long after they had eaten and Stewart was still working on the motor, was the scientist rewarded with a message.

"Help-Hudson-Hudson Bay," came the faint voice. "Do you hear me?" There was a burst of static. Then, "-only one day's food and fuel left-three of us-injured-can't get out."

Professor Wood called to the others to tell them the disturbing news. He begged to be allowed to speak over the transmitter and tell Ms friends help was coming. "I don't want to upset the capture of that criminal you're after, but this trip was originally designed for a different purpose," he reminded the Hardys.

Frank and Joe agreed, but asked that he mention no name but his own. They suggested the professor use the transmitter on the walkie-talkie, since it was more powerful than the one in the plane. Frank tuned it to various frequencies since he had no idea on which one the lost scientists might pick up a message. All the while Professor Wood kept repeating:

"Professor Henderson-Professor Wood speaking-I got your signal-help is coming-• reply if you can hear me."

But there was no reply, though he repeated the message at intervals for over an hour.

"Their receiving set must be dead," concluded the scientist. "Otherwise they would answer me."

In the meantime Stewart had completed taking down the faulty motor. His report was not good. " I can't get this fixed for at least twenty-four hours," he told his companions.

"That may be too late for my friends," replied Professor Wood. " Suppose we set out on foot first thing in the morning. I'm sure we're not far from White Bear River."

"Pretty tough going for a man of your age," said the pilot. " It might take you days. I think you'd better let the Hardy boys handle this."

So it was that at dawn the next day Professor Wood remained at the plane while Frank and Joe set out on skis, carrying the walkie-talkie radio and a supply of food with them.

The brothers were glad they had brought warm clothing with them, and grinned to think how pleased Aunt Gertrude would be to hear this. Although the full bitterness of the northern winter had not yet descended, an icy wind blew across the snow-covered land-a wind that came straight down from the Arctic regions.

All morning the boys trudged onward, keeping due north by their compasses. At the top of each hill they scanned the country ahead, hoping for some glimpse of the river. But it was not until mid-afternoon, when they reached the summit of a long snow-swept ridge, that they saw the water. But there was neither plane nor cabin in sight.

The boys welcomed the chance to rest. Frank turned on the receiver to the frequency the scientists used. For a while they heard nothing. Then came a voice, very faint and weak this time:

"Help-Hudson Bay-White Bear-near the shore--"

That was all. But it was enough to narrow down the field of search. The brothers resumed their journey, keeping the walkie-talkie turned on in case there might be a further message.

Their route led them through a woods. The Hardys were grateful for its shelter from the wind, "but the going was bad. Suddenly Joe's skis came off. It was while he was seated on the ground fixing the straps that the boys heard a snarl. Before Joe could turn, a sleek form made ready to spring at him from a tree.

"Look out!" yelled Frank, but he was too late.

A cunning-eyed lynx leaped on Joe's back. The animal began to claw him viciously.

Frank started to reach for a ski to use as a weapon, but changed his mind; he could not afford to break it. Instead, he yanked the rod-like antenna from the walkie-talkie and slashed at the beast with it as if it were a whip.

The blows told. Cut and bleeding, the animal leaped to the ground, but went in for an assault on Frank. Quick as lightning the youth moved backward, at the same time bringing his metal whip down with full force. It caught the hissing lynx full on the head. The beast crumpled to the ground and lay still.

"Too bad to kill such a beauty," the boy remarked to his brother. "But he sure would have ripped you apart."

Joe was pretty shaken, but he picked himself up. He thanked his brother gratefully, put on his skis and the Hardys set out again,

An hour later they began to feel discouraged, for they had seen nothing resembling a cabin, a plane, or any kind of shelter where the missing scientists or Spike Hudson might be staying. The wind lashed the faces of the boys so hard that at times they had to walk backward.

"I guess we'd better give up," said Frank, out of breath.

"Let's try one more Mil," pleaded Joe, so they went on.

The boys ascended the long, steep slope. When they reached the summit they could see the waters of Hudson Bay in the far distance to the west, and just below them the White Bear River. Joe gave a yell.

"Look! On the river bank!"

His sharp eyes had spied a drifting plume of smoke. It came from a small, crudely-built cabin.

Who was in it? A native, the lost scientists, or Spike Hudson?

"We'd better approach carefully," Frank warned.

"But how?" asked Joe. " There's not a tree in sight to hide behind."

The boys talked it over. Should they wait until dark? No, it was too cold.

"I 'm for taking a chance," said Joe. " There's no plane in sight, and we know both Professor Wood's friends and Spike came by plane. Probably some native lives in the cabin."

Frank was not of the same mind, arguing that both craft could have come down somewhere out of range of their vision. He did agree to go forward, however. "For goodness' sake, be careful, though," he advised, as Joe started off boldly. "If Spike's there, he may level a gun at us!"

The boys' pulses stepped up several beats as they approached the building. While still a good distance from the cabin, Frank trained his binoculars on it.

"A man!" he cried suddenly. " He's elderly, and tall and slender!"

"Then he isn't Spike!" exclaimed Joe.

"He's on a homemade crutch!" added Frank.

The boys rushed down the slope. This, they were sure now, was the refuge of the missing scientists. As they ran toward the little building, the man in the doorway gestured to them in friendliness.

"Thank goodness, someone has come!" he gasped. "We'd given up hope!"

There were three men in the cabin. They were indeed the members of the lost expedition. Emaciated and half-starved, all were suffering from injuries which had made it impossible for any of them to journey overland for help.

Their relief and gratitude when they learned that Professor Wood and the rescue plane were close at hand was unbounded. The boys busied themselves making fresh coffee and providing food from the supply they had carried with them.

The men told the story of how they had lost their way in a storm while returning from the Gobi Desert. Then trouble had developed with the plane and they had been forced to bail out, carrying only their short-wave transmitter and some food with them. Fortunately the cabin stood near the spot where they had parachuted to safety.

"We wondered if anyone would ever hear our radio signals," said Professor Henderson. "The batteries were weak. Toward the last we were beginning to give up hope. And then when the plane flew over yesterday afternoon--"

"A plane?" asked Frank alertly.

"Yes. It went down just over the brow of the next hill. We thought it might be a rescue party. But when no one came, we were afraid the pilot had crashed."

The boys could hardly contain themselves. The plane must have been Spike Hudson's and he had meant to come down-he had not crashed!

"Are you sure it landed near here?" asked Frank eagerly.

"The plane dropped out of sight not more than a mile from here."

The Hardys told about the crook whom they suspected of being in the vicinity, saying they would ski over to the spot at once to find out about it. After grave warnings from the scientists, they left the cabin and went to the top of the hill. At the foot of the slope, in the shelter of a clump of trees, stood a good-sized rustic cabin. There was a white curl of smoke from the chimney, and near the end of a natural landing field was a plane.

Frank adjusted his binoculars with fingers shaking with excitement. Through tile powerful glasses he studied the distant aircraft.

"We 're in luck, Joe," he said tensely. " The chase is over. That's Spike Hudson's plane I"

As he watched, the door of the cabin opened. A man came out, went around to the side of the building for a moment, then returned with an armful of wood. Frank handed Joe the binoculars.

"You can see for yourself who he is," he said grimly.

Joe took the glasses. The rough, unshaven face of the crook came clearly into the field of vision. It was all Frank could do to hold his brother back.

"Go easy. Spike's a clever man, Joe. We must outwit him some other way than just rushing at him."

After talking over the situation, the boys decided to approach the place after dark. First they would drain the fuel out of the man's plane, so he could not take off. Then they would try to capture him. Failing in this, the Hardys would call for help on their short-wave radio.

Excitedly the boys carried out the first part of their plan. Then silently, just before the moon rose, they moved toward the cabin.

CHAPTEE XXV

CALLING ALL CROOKS

Frank and Joe stood perfectly still gazing into a window of Spike Hudson's hide-out. The man had built a log fire before which he sat eating his supper. On the table lay a gun. From the holster on his belt protruded another.

By gestures the brothers indicated to each other that it would be foolhardy to try capturing the crook now. They would wait. The man had a row of radios on a shelf, each one tuned to a different short-wave frequency.

"Calling in all cars," said a police announcer 's voice on one. " The two wanted members of the Hudson gang have been taken into custody. Calling in all cars. The--"

With a cry of anger Spike jumped from his chair, knocking it over. In his haste he brushed a cup and saucer from the table. They crashed to the floor. Whipping the gun from his belt, he aimed it at the offending radio and then whirled around. The Hardys ducked out of sight. Spike did not pull the trigger, however. He stalked about, knocking over several pieces of furniture.

When the racket stopped, the boys peered through the window again. Spike Hudson was doing the most surprising thing they could imagine. He was crying! But his tears were not those of remorse; they were the tears of a man beside himself with rage. He began to stomp about the room again, screaming.

"They'll never get me! No, they'll never find this bird!" he cried out. "Those guys that worked for me. Ha, a bunch of dummies. When I get ready for another racket, I'll hook up with a whole new gang that's got some brains!"

With this he switched off all the radios, removed his jacket and boots, and crawled between the blankets on a cot, a gun at his hand. He left the lamps lighted. His eyes remained wide open.

Frank nudged Joe, pointed to the walkie-talkie, and moved off. This was a prearranged signal. Joe got out his flashlight and put his finger on the switch, ready to use it as a signal at a moment's notice, should Spike turn on his radios.

Out of voice range of the cabin Frank tuned his transmitter to the Royal Mounted Police frequency. Presently on the receiver he was told to "come in." Watching for a warning signal from Joe, Frank quickly told the police the highlights of his story. He asked not only for men to capture the crook but also for a doctor and supplies to take care of the scientists.

Just as he finished giving the location where the police were to come, and asking them not to try to make contact by short-wave with the Hardys for fear of putting Spike on his guard,

Joe swung the beam from his flashlight along the ground. The crook must have turned on his radios, Frank thought.

"I was just in time!" he exulted as he returned to Joe. "Boy, was that close!"

He nodded to his brother. Quietly they went to Spike's plane. It was not until they were within the shelter of its cabin that either spoke.

"Did the police say when they'd get here?" Joe asked.

"They're starting at once," Frank replied.

Just before dawn the boys heard a plane in the distance. Then, as the day broke, several uniformed, fur-coated men came across the snow-covered ground. Spike saw them and made a dash for his plane. As he jumped in, the Hardys overpowered him and a few minutes later the police put him under arrest. There was no more dumbfounded man in all Canada than Spike Hudson when he recognized Frank Hardy, whom he had left bound and gagged in a house outside Bayport.

"I don't get it," he growled. "How did you manage to trail me all the way up here I"

"One part hard work, one part good luck," was all the boy would say.

"I figured I was safe so long as my shortwave set was working," muttered Hudson.

"As a matter of fact," Frank told him, "that was the very thing which caught you."

Spike Hudson did not learn the facts of how short-wave had been his undoing until he was returned to the United States some time later and the story came out at his trial. It was highly sensational, and the newspapers gave much space to the story of how the thefts of electronic equipment and the illegal radio market operations had been broken up by Fenton Hardy and his sons.

The boys also received praise for locating the lost scientists. The story of the men's long fight against cold and hunger, while they lay injured in the cabin on White Bear River, was frontpage news when they were brought out to civilization in Pilot Stewart's repaired plane.

"We never would have been saved if it hadn't been for the short-wave set," said Professor Kemp, as he concluded a radio address on a national network. "And, I might add, if it hadn't been for the Hardy boys who not only heard our calls for help but interpreted them correctly, we probably would be there still."

Even Chet came in for a share of credit in the Spike Hudson case. The evidence Frank had taken from the stuffed fox and hidden in his shoes went a long way toward convicting the entire gang. That evidence, however, had almost disappeared.

"Gee whiz," Chet had said when the boys got home, "there just wouldn't have been any case against that bunch if it hadn't been for me. When you phoned and asked me to go out to the airport to pick up your car, I moved in a hurry. Good thing I did, too, because when I got to the parking place your roadster was just pulling out."

"You mean somebody tried to steal it?" asked Frank.

"Sure thing," said Chet. "I hopped on the running board and grabbed the thief before he could get away. He turned out to be one of the Hudson gang."

"That's swell. Well, how's the taxidermy business?" asked Joe.

"Believe it or not, I finished that deer," declared his stout chum. "Looks like a real professional job, too. Come up and see it."

When the boys looked at the mounted deer, they had to admit that Chet had done a great deal better than they had expected he would. The animal was no longer lopsided or bulgy. Chet strutted up and down with his thumbs in his belt.

"It's just a knack," he said. "A little difficult at first, but after a while it came to me."

Just then young Jimmy Gordon and his friend Mickey came into the studio. First they had to hear all about the adventures of the Hardy boys in the north country; then Jimmy said:

"What do you think of our stuffed deer!"

"They've seen it," said Chet hastily, and tried to change the subject.

But Jimmy did not take the hint. "Mickey and I helped with the deer," he said. "We worked hard on it to surprise you when you came back."

"And what did Chet do?"

"Oh, he sat on the table and read the directions to us."

Chet's embarrassment at having been given &way did not last long, because at this point the Hardys presented him with an otter they had bought from an Indian at a northern trading post, and the fat boy vowed he would do every t>it of taxidermy work on it himself.

"And there's a gift coming to you, Jimmy, for helping us solve the mystery," said Frank. "We suggest you let Mickey play with it often."

The youngsters were escorted to the Hardy attic and there presented with the brothers' toy electric train set. Jimmy's eyes nearly popped from his head.

"For me?" he gasped. "Oh, gee, thanks. And any time you want any more detecting done, let me know!"

That night Professor Wood came to the Hardy home to dinner. Mrs. Hardy had returned and the occasion was something of a reunion. During the meal her husband told the inside story of the round-up of the Hudson gang.

"What I want to know," said Chet, who was there by special invitation, "is who locked up Professor Wood in the taxidermy shop?" The boy passed his plate up to Fenton Hardy. "Thank you. I could do with a second helping of that roast, Mr. Hardy."

The detective heaped the boy's plate with, food.

"It was Billy Batter who attacked Professor Wood," he said. " Mr. Gordon, Jimmy's father, happened to mention to him about the stuffed animals being here. Batter thought he saw a good chance to steal some of them.

"In the meantime, he learned that Hardy and Sons were after the Hudson gang, "o he got the idea we might be frightened off the case if he kidnapped Chet for a while. So he came to the taxidermy shop one day when he knew Frank and Joe were out and Chet would be alone. But Chet wasn't around, so he waited. When Professor Wood came in unexpectedly, he had to get him out of the way.

"Still Chet didn't return. A little later Batter heard Frank and Joe coming across the yard. He knew he couldn't handle both of them, so he picked up the bear cub, dropped out the window, and ran away. He had already put the kidnap note on the door before the professor came, and forgot to take it down."

"It's unfortunate I didn't see it," said the scientist.

"Tell me something," asked Aunt Gertrude. "Who thought up the idea of placing the shortwave sets in the stuffed animals?"

"Batter again," explained Mr. Hardy. " And he also suggested putting the animals around the grounds of Hudson's estate to frighten off intruders."

"But Spike Hudson was the brains of the gang, wasn't he?" asked Professor Wood.

"Oh, yes. He thought up the system of cod(c) signals to direct the thieves' work and disposed of the radios they made from the stolen parts."

"How about the wallet we found near the dock at the Cooper factory?" asked Joe.

"An ex-convict named Rugby worked for Hudson, ^.e was the 'lookout' for the gang. He had stolen the wallet. After taking the money out of it, he threw it away."

"Was he the one who took our boat after the watchman knocked me out?" asked Frank.

"Yes. When things were getting hot at the factory, the thieves were afraid to take the stolen quartz crystals away in the truck, so they piled them in the boat and Rugby delivered them at a safe place on Barmet Bay. Then he &et the boat adrift. By the way, he was the one who was driving the truck when Batter accidentally lost that little scrap of envelope and paper that gave you boys a lead to his address."

"That seems to clear up everything," said Frank, and added hopefully, "I wonder when the next mystery will come along for us to solve."

Of course, since the Hardy boys were to be involved, one was to follow right on the heels of the short-wave case. Chet dubbed it "The Secret Panel."

"I hope there won't be another mystery," sniffed Aunt Gertrude. "Too much wear and tear on my nerves. I can hardly turn on the radio without wondering if I'm not going to Jiear some sort of code message to a gang of crooks."

Mr. Hardy smiled. "The only mystery I can think of at the moment is what is in that package which arrived by express just before dinner. It's from Washington and it's addressed to the Hardy boys."

Frank led the scramble from the table. Chet and Joe helped him unwrap the box. There was a note inside.

"A personal gift to two fine young detectives," it said. The note was signed by an official of the F.B.I. And inside the package was a compact two-way radio outfit that the boys stared at in delight.

"A television walkie-talkie!" whooped Joe.

"I believe I'll keep this right in the house," laughed Mrs. Hardy, who had come up behind them. "Then maybe I can keep track of my two famous boys!"

THE END