Also In This Series

By Kenneth Robeson

#1: JUSTICE, INC.

#2: THE YELLOW HOARD

WARNER PAPERBACK LIBRARY

WARNER PAPERBACK LIBRARY EDITION

FIRST PRINTING: AUGUST, 1972

COPYRIGHT © 1939 BY STREET & SMITH PUBLICATIONS, INC.

COPYRIGHT RENEWED 1969 BY THE CONDÉ NEST PUBLICATIONS, INC.

ALL RIGHTS RESERVED

THIS WARNER PAPERBACK LIBRARY EDITION IS PUBLISHED BY

ARRANGEMENT WITH THE CONDÉ NEST PUBLICATIONS. INC.

COVER ILLUSTRATION BY PETER CARAS

WARNER PAPERBACK LIBRARY IS A DIVISION OF WARNER BOOKS,

75 ROCKERFELLER PLAZA, N.Y. 10019.

A Warner Communications Company

ISBN: 0-446-64-898-1

Printed in the United States of America

CONTENTS

THE SKY WALKER

CHAPTER I: The Noise From The Sky!

CHAPTER II: The Avenger!

CHAPTER III: Death Masks a Secret!

CHAPTER IV: The Sky Walker!

CHAPTER V: Trapped!

CHAPTER VI: Trickery Succeeds!

CHAPTER VII: Death—Odds-On Favorite!

CHAPTER VIII: Cold Extra!

CHAPTER IX: The Bears’ Den!

CHAPTER X: The Flying Dutchman!

CHAPTER XI: Strange Revelations!

CHAPTER XII: Murder Stroke!

CHAPTER XIII: No Sale—No Suspect

CHAPTER XIV: Murder Rides The Rails!

CHAPTER XV: The Boss!

CHAPTER XVI: Invention—A Crook’s Tool!

CHAPTER XVII: Twins—One Killer

CHAPTER XVIII: Backfire!

THE

SKY WALKER

CHAPTER I

The Noise From The Sky!

It was half past three in the afternoon. That is a little early for the cocktail hour, so there weren’t many people in Mike’s Tavern. There were enough to provide plenty of witnesses, however. And all were witnesses, because all saw the crazy thing that happened, that day in Chicago.

Mike’s Tavern is on Belmont Avenue, not far from Lincoln Park. Probably the location was the reason why the thing happened there, because the source of the weird trouble was later disclosed to have been Lincoln Park. At least, that was as close as they could narrow it down.

Four men and a couple of women were sitting on the leather-covered chromium stools along the bar at Mike’s. Five of the six had drinks in front of them. The sixth had finished his and ordered another. A martini. He had already had too many martinis; so when the thing happened the first time, the rest just laughed at him and said he was drunk.

He had the empty cocktail glass in his hand and was twiddling it around by the stem while Mike, the bartender, poured amber fluid into a fresh glass.

And the glass the man held on the bar suddenly went to pieces!

There was a sound from it first. A thin, wailing sound, as if a violin note had been played nearby and the glass was resonating to it. The thin, wailing sound ended in a sharp pinggg, and the glass seemed to explode in his hand.

For a few seconds the rest were surprised into silence. Then the man sitting next to him laughed.

“You’ve had enough,” he said. “Breaking a glass like that. What’d you do—hit it against the bar?”

The man whose glass had broken was staring stupidly at the pieces.

“I didn’t break it,” he said. His eyes were wide and staring, with something like horror in them. “I didn’t hit it against anything. I was just holding it.”

“Then you squeezed it too hard,” his friend taunted. “Boy, you don’t know your own strength.”

“I didn’t squeeze it! I didn’t do anything to it. It just gave a kind of funny sound and broke.”

“Go on—something had to make it break—”

On the shelf behind the bartender was a row of similar glasses. There were eighteen or twenty of them. The man who was speaking had suddenly stopped his words, because the row of glasses had started to sing.

From each of them was coming the thin wail of sound that had preceded the breaking of the glass the man held. It was uncanny; as if the glasses had abruptly come alive. They shrieked like little lost souls, and then broke!

Every last one of them broke, as if each had been hit squarely by a small bullet that shattered it to a thousand pieces.

“Well!” said Mike, the bartender, eyes goggling. “That ain’t the fault of anybody who’s had a few too many!”

They all stared at the fragments. And all felt a chill, creepy sensation as they looked. Glasses don’t just sing, and then break—all by themselves. But these had.

It was at about this time that the seven in the place began to hear the sound from outside. In the sky, it seemed. It was a loud, steady drone, like the snarl of a motor. Like an airplane motor, save that it seemed to be snarling a shade more shrilly than the usual plane motor.

They paid little attention to it. Planes over Chicago are too frequent. Anyway, they were too busy looking at the glasses. A score of empty cocktail glasses, with no human hand near them, that had sung a weird, small dirge and then died in a thousand fragments.

Outside the tavern, people were paying plenty of attention to the sound from the sky. At any rate, they all swore later it had come from the sky. At first, people paid little heed because they, too, had figured it was just the noise of a plane motor, and such noises are common to a big city. But then a few began craning their necks to look up into the sky; then a few more did the same, and pretty soon everyone around was doing it.

Crowds looking into the sky, and then staring at each other, and finally staring back up again. The faces of most of them were a bit pale, and all of them showed perplexity.

There wasn’t anything up there to see!

The droning sound was about like that of a fast-moving plane, much lower down than the transports fly. But there was no plane to be seen in the heavens. It was a cloudless, sunny afternoon, too.

The sound from the sky stayed over Lincoln Park. It seemed to move in a wide circle, since it was loudest first at the north end of the park and then at the south end. It faded a little and gained a little, as if whatever made it came now nearer the ground and now higher.

But all the time there was not one thing in the empty heavens to make the sound.

Down in the news offices of Chicago’s biggest newspaper, the Daily Record, the city editor began to think the whole town was going crazy. That was because of the telephone calls that suddenly began pouring in.

It seemed that Mike wasn’t the only person who had had glasses sing and break. A score of people phoned in similar accounts. A woman had been looking at a picture, and the glass over it had suddenly shivered into bits. A man had been lifting a water tumbler to his lips when it abruptly acted like a bomb and went off in his hand. Several big plate-glass windows shattered. And all these things happened with no human hand near enough to account for the violence.

Each person telephoning the paper and demanding an explanation reported, as an afterthought, hearing the droning noise in the sky.

So many people phoned that, crazy as it all sounded, the editor put a veteran reporter on it. Of such things are interesting items made.

The droning sound, heard loudest over Lincoln Park, had been heard in the Loop, Chicago’s downtown section, too. The reporter assigned to the story had heard it.

“Hell, it’s just a passenger transport,” he said. “Something funny about the pitch of the motor is breaking glass.”

However, no airplane motor had ever had results like that before. And there was always the undeniable fact that there was, after all, no plane in the sky to see.

The reporter phoned Fort Sheridan, north of Chicago. Their radio operator promised to send two army ships to the area and have them investigate. After all, planes must have licenses, and if some mysterious flier was stunting around Chicago, they wanted to know it.

The army ships got down to Lincoln Park within a quarter of an hour. They got down there while the droning noise was still coming from the sky. They flew around the place like excited hens hunting for chicks near a duckpond.

And they saw just what people on the ground saw.

Which was nothing at all. Noise was coming from the sky, but there was nothing in the sky to make the noise.

The veteran reporter phoned Northwestern University, and professors there studied the seismograph in the laboratory. The delicate instrument reported no earth tremors of any sort. The sound, it seemed, was coming from nothing connected with the ground.

Then the noise faded out, as unexplainably as it had faded in. There was no more droning sound, and no more glass around Lincoln Park sang a tortured shrill song and broke.

The reporter kept on doing his job. He got in touch with various city engineers and scientists to get their theories about it all. He was beginning to think the whole business was a great joke by now.

He got a flock of theories.

A prominent engineer said that the upper atmosphere was heavy and dense in spite of the cloudlessness of the sky. It caught the noise of a boiler blowoff out west on Belmont Avenue, resonated and echoed the sound of the escaping steam, and produced the queer droning noise.

A scientist at Northwestern University said that perhaps the sound had been reflected from far away. A plane, perhaps a hundred miles off, was the source of the sound. Then the noise had traveled along under the stratosphere, bounced along like a golf ball on hard pavement, till it was heard in Chicago.

It was, he explained, like the transmission of an image for a hundred miles in a mirage, only in this case a sound and not an image had been transmitted.

The commissioner of parks had the most natural-sounding explanation.

Nearly all of Lincoln Park was torn up with a new boulevard plan. Lots of pneumatic drills and hammers were working. The commissioner thought they’d all joined in in a huge diapason, and the sound had swelled into a drone that seemed to come from the sky.

Nobody came within a million miles of the truth. And no one treated the sound, after it was over, as anything other than a slightly uncanny jest.

The city forgot it in the news of the early evening.

Near the south end of the park, not far from the statue of Lincoln, a new pavilion had been erected in a strategic spot. It was two floors tall, a shell of steel and prefabricated material. The top floor was open, and it was a nice place to sit in the evening. Benches were up there.

A couple of dozen people were sitting there the evening of the day when the noise had been heard. They weren’t moving around much; were doing nothing to shake the pavilion in any way.

But, just the same, the pavilion acted as if they’d somehow strained it beyond capacity. For suddenly the structure collapsed.

There was no warning sound of any kind. There was no preliminary tremor. The pavilion simply collapsed!

There was a growing roar as tons of steel and material began grinding together as it twisted and sank in a heap. The roar had overtones of shrill horror from the humans trapped on the top floor. There was a final crash and a cloud of dust. Then there was terrible silence.

People ran toward it. Police came up on motorcycles and in squad cars. An ambulance clanged there in a hurry, followed by three more. But there was more need for death cars than for ambulances.

Of the people who had been in the pavilion, only six were alive, and they were hideously mangled. The rest, seventeen, were dead, crushed by the girders.

The cops began poking around in the debris.

As they looked, their mouths began to take on a grimmer line, and their eyes grew bleak. It was the way they looked when they investigated the trail of a murderer. And, as far as they could see, that was just what they were doing. Only in this case the murderer seemed not to be a lawless individual, but a highly respected, great corporation.

They were examining the girders, when their faces took on that look. The girders supplied by the corporation.

The heavy, steel I-beams looked as if they had been made out of soft wood that had been riddled by termites. The steel seemed to have a cheesy, granular structure, that was flawed and cracked in countless places.

The metal, supposed to be tough and dense, looked like brittle glass that had been dropped and shattered.

“So that’s the kind of junk the city gets on a big job,” growled one of the cops.

“No wonder it fell down!” another jerked out. “Why, it’s murder, that’s what it is!”

A great tragedy coming close on the heels of a joke. And drowning out all memory of the joke.

A mere noise in the sky couldn’t be expected to hold the news limelight when a pavilion had collapsed and killed seventeen people.

CHAPTER II

The Avenger!

At thirty thousand feet, a big plane lanced along a beautifully deft straight line from New York toward Chicago.

The ship was much like the new army bombers, the flying fortresses. But it was a private plane, and it had new features that even the bombers don’t possess. For one thing, the cabin was hermetically sealed, and there was an oxygen-manufacturing machine behind the instrument panel that was better than any oxygen-making apparatus seen before. This enabled the plane to fly high in the stratosphere.

For another thing, the motors had not only the last word in superchargers, but also had variable-control cooling systems, so that in the subzero temperatures of great altitude some of the cooling surfaces could be cut out and the cylinders kept hot.

Finally, the plane was equipped with special, four-bladed, variable-pitch propellers designed by one of the world’s great experts in aerodynamics, Richard Henry Benson.

Dick Benson was at the controls of the flying marvel now.

Even seated, the man called The Avenger was an impressive figure. He had lost his beloved wife and small daughter in the callous machinations of a criminal ring—which loss had impelled him to dedicate his life and his great fortune to the fighting of the underworld. The tragedy had turned his coal-black hair dead white. Also, the nerve shock had paralyzed his facial muscles in some curious way which made the dead flesh like wax; it could not move at the command of his nerves, but when his fingers moved it, it stayed in whatever place it was prodded. Thus he became a man of a thousand faces, for he could mold the obedient plastic of his countenance into the shape of the faces of others, and pass as them.

From the dead-white, immobile face under the snow-white hair, pale-gray eyes flamed forth. They were awe-inspiring, those pallid, deadly eyes. They were as cold as ice in a polar dawn and as menacing as the steel of dagger blades. They were the almost colorless orbs of an infallible marksman and of a person without pity for enemies.

They were, in a phrase, the eyes of a machine rather than a human being.

Benson got up from the controls, and went back into the hermetically sealed cabin, allowing the ship to fly itself. It could do so very easily, such were the automatic devices standing ready to take over stabilization and course charted.

The man with the dead face and the silver-white hair went back to where the others in the plane sat in a group. These others, associates of his, were as remarkable in their way as he was in his.

There was Smitty, fully named Algernon Heathcote Smith and hating it. Smitty was colossal—six feet nine inches tall, weighing just short of three hundred pounds.

The vast barrel of his chest was so muscled that his arms wouldn’t hang straight at his sides, but were crooked like those of a gorilla. With china-blue eyes beaming from a moon-face, he looked as harmless as he was huge; but appearances in his case were very deceptive indeed.

There was Fergus MacMurdie, a dour Scot with bitter blue eyes and sandy-red hair and great dim freckles that could be seen under the surface of his reddish skin. He had the biggest feet and the biggest and most formidable fists in captivity. MacMurdie had been set up in business in New York’s strangest drugstore by Benson. But when a battle against crooks loomed near, Mac left the store in a hurry. He had suffered from criminals as much as his chief, and he was as grimly glad to fight them as Benson was.

Finally, there was a figure looking as dainty and fragile as a Dresden doll when seen next to the tremendous bulk of Smitty and the gangling length of MacMurdie. This was Nellie Gray, whose kindly professor father had been murdered by the underworld, and who had become one with this small band of bitter crime fighters. She was just a shade over five feet in height and just a little over a hundred pounds in weight, and she was pink-and-white and helpless-appearing.

But men have been known to lay hands on her and get a sudden impression that they had grasped a stick of dynamite.

Smitty and Nellie were staring out the double windows and down at a world bathed in nine-o’clock darkness. It was still dusk at thirty thousand feet.

MacMurdie was looking at a news report that had come to Benson at seven o’clock. The Avenger was on the cable and wire list of every news-gathering agency on earth. Their reports went to newspapers, state department—and Benson.

“I’ve never seen ye make up your mind to move so fast as ye did tonight, Muster Benson,” Mac said in his thick Scotch burr. “Ye seem very sure something big and deadly hangs over Chicago.”

Benson sat down in the seat next to him. Though not a large man, Benson gave an impression of tremendous power. He moved like a gray cougar; and when he relaxed, he seemed to sink into a dynamic repose that could be shattered with violent action in a fraction of a second.

“I’m sure of it, Mac,” he said. His voice was vibrant and compelling. “Here is a brand-new steel structure. It is only two stories in height, so there is no great stress on it. It is designed to hold several hundred people, and it collapses under the weight of only a few dozen. The report is that the girders were faulty. But steel girders couldn’t possibly be as faulty as that.”

“Do you think the weird noise from the sky has something to do with it?” asked Nellie, in her sweet, soft voice.

Benson’s eyes were pale, cold flames.

“The sound was odd and unexplainable. The collapse of the pavilion was odd and unexplainable. The two things occurred only a short time apart. The inference is that they were tied in together. The inference also is that the two things were cold-bloodedly planned. And seventeen are now dead because of it! So we’re on our way to look around and possibly prevent the deaths of seventeen—or seventy—more—”

At Chicago police headquarters a maniac was trying to see the commissioner.

He was a little man with a big head and bifocal glasses so powerful that they made his black eyes seem to bulge out till they could have been knocked off with a stick. He had thin gray hair and no hat. He didn’t have a coat on, either, and a chemical-stained vest was his only protection against the fall-night coolness.

“I tell you I’ve got to see him!” the little man cried to the sergeant barring his way in the first-floor hall. “If he’s at home at this hour, I’ll go there—”

“He’s not at home; he’s here,” the sergeant admitted. “But he’s too busy to see anybody. He’s got some city engineers and a brace of steel men up in his office. He’s workin’ on that pavilion collapse.”

“But it’s about that that I must see him!” the little man shrilled. “That, and the noise in the sky. I can tell him things about both that he must know.”

“You know something about them,” said the sergeant. It was not unnatural that his voice and face were suspicious. So many cranks come to a big-city police headquarters. Let a notorious murder be done, and a dozen crackpots rush in to tell all about it. Many of them even confess to it—only the psychologists know why.

“I know all about them,” said the little man. “They are inventions. But I must see the commissioner. He’s the man who should know these things.”

“I tell you—” the sergeant began doggedly.

The little man’s hair was standing on end. He passed a frenzied hand through it, further increasing its wild disorder.

“But this can’t wait! No matter what he’s doing—he must drop it and listen to me! There may be more tragedies if he doesn’t!”

“Who are you, anyway?” the sergeant growled.

“I’m Maximus R. Gant, inventor. I live with Robert Gant, my brother. He’s an inventor, too.”

The sergeant rasped at his jaw with an uncertain hand.

“You’re meanin’ to say that some invention was what made the noise in the sky? And it made the pavilion collapse?”

“Yes!”

“And you and your brother have something to do with the inventions?”

“We have everything to do with them. And I’ll tell the commissioner all about it if you’ll just get me into his office.”

The sergeant sighed. “So help me, if this isn’t as important as you say, it’ll be my head. But I’ll interrupt him on the chance—”

The door swung. From the main hall the sergeant could see a white car outside. It was like a small truck, but it had windows, and the windows had heavy grating over them.

The door had opened to admit two men who had come from the white car. The men were in white, too. They looked like internes from a hospital, but they had on white caps. They were muscular men with hard faces.

“Uh-huh,” one said. “There he is. I thought he’d break for headquarters.”

“We’re going to have to keep him in a strait jacket if he doesn’t stop escaping,” the other said. “He’s a clever one, all right.”

The two men in white were walking toward the little man with the thick glasses and the sergeant. But their eyes were only on the little man, and their eyes were wary. The little man stared back with almost stupid surprise in his face.

“Hey!” exclaimed the sergeant. “What—”

He stopped there. His face showed that he’d gotten the whole story with one look at the white uniforms of the men.

“What has Thomas Edison been telling you?” said one of the two attendants. They had stopped on each side of the little man, and had a hand on each of his scrawny arms.

“Thomas Edison?” repeated the sergeant.

“Sure! That’s who he thinks he is—Edison. So we give him some chemicals to mess with and cogwheels to play with, and everybody’s happy. Except that now and then the little runt climbs over the wall and gets away.”

“You mean he’s a lunatic?” said the sergeant.

On the little man’s face the expression of startled surprise was giving way to fear. An awful fear!

“No!” he gasped suddenly. “These men are lying! I’ve never seen them before. I’m not mad—and they’re not from any asylum.”

“Come along, Tommy,” wheedled one of the men in white, impelling him toward the door.

The little man began to struggle wildly.

“No! No! Officer, don’t let them do this! They’re going to kill me!”

One of the men in white shrugged, and grinned a little at the sergeant, who drew a profound breath of relief.

“And I was just goin’ in to the commissioner with this nut’s story! And him busy as an ant in a wasp’s nest! I’m sure glad you boys came along when you did.”

“You’ve got to listen!” shrieked the little man. “These two are murderers! You hear? They want to get me away before I can tell what I know. They mean to kill me! You’ve got to stop them. Call the institution they’re supposed to be from. You’ll find no one like me is registered there. And you’ll find that no one like these two works there. Please! That’s the least you can do.”

“Now, Tommy,” soothed one of the men, “come along and stop calling us names. We’ve got a new pot of chemicals for you to experiment with, and you haven’t yet finished that job on perpetual motion—”

They had him, screaming and dragging back, at the outer door. The sergeant rasped his jaw undecidedly, then winked at them.

“Hope you don’t have too much trouble gettin’ him back,” he said.

“We won’t,” one of the men in white retorted, doubling a thick arm suggestively.

They got the little man into the whitewalled car. His frantic face appeared at the grated window nearest the sidewalk.

“Help! Help!” his muffled voice came to passersby who had stopped to watch out of curiosity and sympathy.

The padded truck rolled away.

Up at the wheel, one of the men in white sent the car north. In the body of the car, with the little man, the other fellow in white suddenly lashed out with a malletlike fist. The little man’s glasses splintered and cut his face, and he went down, a pathetic, small figure sprawled on the padded floor of the asylum ambulance.

“Going to spill the beans, eh?” the man snarled at the prone figure. “Just about to cut in on the commissioner, eh? Two more minutes— But we got to you in time.”

The light truck went north and then west. When it had come to a wooded spot twenty miles out, the man in the rear got an automatic from under his white jacket. He waited. In a few minutes a single toot from the horn showed that the driver had looked up and down the road and no other machine was in sight.

The man shot the little fellow through the head.

The car turned into a woods road a few miles farther on. There was a sedan there. The men got out of their whites and left them in the white car. They got into regular clothes, climbed into the sedan, and drove off.

Not for nearly ten hours was the car, stolen from the Belgrade Sanitorium, discovered with the dead man in it. One key that might have unlocked the riddle of the noise in the empty sky was destroyed.

CHAPTER III

Death Masks a Secret!

The house was huge, old-fashioned, of frame. It was set in a woodlot, the trees of which cut off sight and sound from the nearest habitation. The men who moved furtively among the trees knew all about that. They had studied this place, north and west of Chicago, before coming out. When you plan to murder somebody, you look over the spot beforehand if you are good at your trade as killer. And these men were good!

They slid in the midnight darkness among the trees as silently as Indians. Each had a gun in his hand!

A man’s shape suddenly loomed in front of one of the four killers as the house was neared. The man was in overalls, was gardener here. He started to let out a startled shout. The man nearest him brought his gun barrel down on the gardener’s head. The gardener fell, killed instantly by the heavy blow. The four men went on.

In the house, there was worried silence. There were three people in there. One was a very tall, very thin colored man in a white housecoat. Another was a slenderly rounded Negress with intelligent, liquid eyes—his wife. The third was master of the house.

This third man looked a great deal like the little fellow with the thick glasses who had been taken away from police headquarters in the fake asylum car. He was taller and heavier, but he had the same nearsighted black eyes and the same lank gray hair. He was the murdered little man’s brother, Robert Gant. And the thing he was worrying about now was the continued absence of that brother.

“He should have been back, or at least have phoned, long before now, Joshua,” he said to the colored man.

“Yes, sir, he should,” nodded the colored man. There was no accent or Southern slurring of his words. He spoke like an educated person—as, indeed, he was. Joshua Elijah Newton had graduated with high honors from Tuskegee Institute. So had Rosabel, his wife.

“He said he was going straight to police headquarters, and would come straight back,” worried Robert Gant.

Joshua only nodded again. Normally Josh moved so slowly, and kept his eyelids dropping over his eyes so somnolently that he was nicknamed Sleepy. Normally, too, he talked with the “suhs” and the “Ahs” instead of “ers” that most colored people use.

But now his speech was crisp and correct, and his dark face was alert and shrewd with the worry he shared with his master.

Rosabel, the pretty Negress who, with Josh, took care of the two childlike brothers who spent their lives inventing things, broke in.

“Don’t you think you’d better phone the police, Mr. Gant?”

Gant bit his lip. His face was a study in indecision.

“Well, Rosabel, you know how we feel about the police,” he said at last. “We haven’t wanted anyone—not even the police—to get a hint of what we’re working on. So we’ve left them severely alone. Even after that outrageous theft of a month ago, we didn’t notify the police. We’ve been trying on our own to get the things back. I hate to break that policy now.”

“But Mr. Max Gant went to headquarters intending to tell all about it,” Rosabel pointed out. “So why wouldn’t it be all right for you to phone them now?”

Gant shook his head uneasily.

“I suppose it would. But if the world should learn— What was that?”

He was listening intently. Joshua and Rosabel listened, too.

“What was what, sir?” Josh said, after a moment.

“I thought I heard someone at the door.”

“We have Peter, the gardener, stationed outside on the grounds,” Josh said. “If anyone were trying to get at the door, Pete would have sounded an alarm.”

“I suppose that’s true,” Gant murmured. “When you own a secret such as we do, the least sound is suspicious.”

He had been pacing up and down the living room on the first floor. He went to the hall door.

“I’m going up to the laboratory. You watch down here. If you hear anything, call for help. I’ll phone Chicago headquarters promptly at twelve o’clock—in fifteen minutes, that is—if Max isn’t back.”

He went out, and they heard his steps on the stairs.

Josh’s long dark hand went out to cover Rosabel’s lighter one. There was a very close bond between these two.

“We’re in danger,” Josh said to his wife. “I can positively smell it. We’ve been in danger since somebody broke into the house and took what Mr. Robert and Mr. Max were working on, a month ago. But it’s worse tonight.”

“Why would it be worse tonight?” said Rosabel, trim and competent-looking in her maid’s white apron with a small white cap on her black hair.

“I believe they’ve been watching this house—whoever they are,” said Josh. “I believe they knew when Mr. Max went out to go to the police. If that’s true, they might decide to shut Mr. Max and Mr. Robert up, forever, tonight.”

“Then Mr. Robert should have phoned the police hours ago!”

“I think he should have, honey,” Josh said. “But we can’t try to tell him his business—”

He stopped, and the two stared at each other with the whites of their eyes showing, and then stared toward the hall.

There had been a hard, brisk knock at the front door.

“Josh— Don’t go to it!”

“It may be Mr. Max coming back. I’ve got to go.”

“He has a key.”

“You know how he is,” said Josh, almost like a parent speaking of a child. “He’s always forgetting his keys. I’ll just call through the door. I won’t open it.”

He went to the hall, thin and spindling and six feet two, with pretty Rosabel after him.

“Who’s deah?” he called through the door.

When Joshua Elijah Newton was uncertain of the person he was talking to, he instinctively dropped into the kind of talk you expected from a colored man, and looked rather slow-witted and stupid. So did Rosabel. It was good protective coloration. It threw others off their guard.

“Josh! It’s me. Open up.”

“It’s Mr. Max,” said Josh with a sigh of relief. His long thin hand went toward the door bolt.

Rosabel caught it almost fiercely.

“That’s not Mr. Max’s voice!” she whispered.

“It sounded like him—”

From the living room they had just left came a thin snap of breaking glass, where a windowpane had been cut and then tapped out. But the two did not hear, with their attention distracted by the man at the door.

“Josh! Open up, I said,” came the call through the door. “I forgot my keys.”

“You’re right,” Josh whispered to Rosabel. “It’s not Mr. Max’s voice. Run and phone the police, honey. I’ll try to hold him out there till they come.” He raised his voice, “Yas, suh, Mr. Max. But I haven’t the key, myself. Mr. Robert has it. I’ll go up and get it.”

Rosabel was racing for the phone. Her path lay past the living-room doorway.

As she passed the door, arms reached out. A hand was clamped over her lips, and a forearm was crooked brutally around her slim dark throat.

Another man passed her and the fellow holding her and sneaked toward Josh, who had his back toward the hall. Josh was making stamping noises with his feet, like a man going up the hall. This was to fool the person outside into thinking he was going for the doorkey.

With a furious burst of lithe energy, Rosabel got clear of the hand over her lips for just an instant.

“Josh!” she screamed.

Josh whirled. But he was just a little late. The man who had been skulking toward him was within leaping distance. His gun hit Josh’s head a glancing blow. He got the door unbolted.

Josh fought like a black cat, but he hadn’t a chance. Two more men came in the front door. The man who had caught Rosabel dropped her limp body, as she went unconscious from strangulation. The four steam-rollered over the colored man and he, too, lay unconscious on the floor.

One of the four pointed his gun speculatively.

“Do we blast these two smokes?” he said.

Another hesitated, then shrugged. “Guess not. No use making any more noise than we have to. They wouldn’t know what goes on in the laboratory upstairs. The guy, Gant, is all we’re told to get. We got the brother; now we’ll take him, and the job’s done.”

They trooped up the stairs.

The laboratory of the Gant brothers was on the top floor of the three-story house under the eaves. It was a big room with workbenches around the walls. Robert Gant was near the door.

“Josh?” he said inquiringly, as the knob turned.

It was the last sound he ever made.

Killers who know their trade take no chances. Three of the four gunmen shot him from the door, pouring lead into his staggering body from their guns.

They stepped over him and went methodically around the laboratory smashing things. They broke apparatus and tubes and jars. They upset tables and benches. But because they themselves didn’t know quite what it was they were to destroy, they left a couple of things that they should have ruined.

One was a large, flat pan with colorless fluid in it. The other was a stack of oblong glass panes, about four inches long and one inch wide, next to the pan.

These things seemed meaningless so they didn’t destroy them or disturb their juxtaposition.

“That’s all,” said the leader of the four. “We better lam now. Those shots must have been heard around here.”

They fled down the stairs. There was a flat roar of a gun, and the leader fell without a twitch, with a bullet in his head.

The gun was in the hands of Josh Newton.

There is a fierce loyalty in men, if they are the right sort. And this long, thin colored man, who looked sleepy and slow-witted under normal circumstances, was very much the right sort.

He had come to in time to hear the last of the crashing destruction on the top floor. He must have known that his employer lay dead. Hence there was nothing more he could do. Common sense should have told him to take to his heels and save himself.

But the colored man wasn’t built that way.

There was an old-fashioned .38 revolver in the library. He’d gotten that. And now one of the four men had paid with his life for what he had done.

The other three swore with murderous surprise and cut down on him. Josh stood by the door, making no effort to hide his thin body. The shot of one of the three went over his head. Another sliced past his side. The third had had a better aim and might have drilled his head. But just before the third was dispatched, Rosabel rose up beside the stairs, where the banisters had hidden her.

She had a vase in her tapering, competent hand. The vase broke over this third man’s head, and his shot went into the hall ceiling. But that was the end.

Both men left on their feet took their time on the next aim. This would get the colored man.

There was an almost inaudible but vicious little spat of sound from the library doorway, and one of the men went down with a gash on the exact top of his head where a small-caliber bullet had creased him.

The second man jerked around in fright and fury. There was another little spat. And he fell, too; again with the small gash in the exact center of the top of the head.

It had been the end, but not for Josh.

The colored man stared at the library doorway with the whites of his eyes showing. That intervention in the face of certain death had seemed like something from heaven. But the intervener was mortal, it seemed. Though a most unusual mortal.

A man stepped lithely from the library and stared at Josh out of almost colorless eyes that were icily flaming in a dead, white face. In his hands this man had the most curious gun Josh had ever seen. It looked more like a slim length of blue-steel pipe than a gun, with a slight bend for a handle and a small bulge where a cylinder held four shells.

But more terrible than any gun was the man’s absolutely immobile countenance—like a wax mask of death in which steel-gray eyes glared forth.

Following this man came a giant whose head seemed to scrape the ceiling, and whose muscular bulk was such that his massive arms could not hang straight down. After the giant stepped a man with dour Scotch blue eyes and sandy-red hair; a man about as tall as Josh and almost as thin.

Josh stared at the three, and Rosabel ran to his side. They’d downed the gunmen, but she couldn’t be sure they were not enemies, too.

The man with the deadly, pale eyes spoke crisply.

“You two are the servants in this house?”

“Yas, suh,” said Josh.

“Where is Robert Gant?”

“I’se skeered he’s daid, upstairs,” said Josh.

“And Maximus Gant hasn’t come back yet?”

“No, suh.”

The man with the dead face turned to the giant.

“Max Gant is dead, then,” he said to the big fellow. “When I radioed headquarters from the plane before landing, and they told me about the lunatic being taken away, I was certain of it. And now we’ve come here too late to save the brother.”

“It’s obvious that they were killed to keep some secret, but what it was, we’ll never know,” the giant said pessimistically.

“Maybe we can learn something in the laboratory.”

“They-all busted up the lab’tory somethin’ turrible,” said Josh to the man with the awesome eyes.

The eyes turned on him in all their clarity, and the colored man had the swift feeling that they were going clear through him.

“You don’t have to talk that way,” the man said to Josh. “You’re very well educated.”

“I’se talkin’ nachral—”

“The little gold key I see between the third and fourth buttons of your jacket tells a different story.”

Josh hurriedly shoved the mentioned article back under his house coat. Then he relaxed.

“Very well, sir. These murderers, I’m afraid, have completely wrecked the laboratory. May I ask who you are?”

“My name is Henry Benson.”

It was enough. Josh was as well informed in current events as he was in scholastic subjects. He stared with rolling eyeballs at the grim, white mask of a face.

“The Avenger!” He and Rosabel looked at each other.

“Some call me that,” said Benson. “Now we’ll have a look at that laboratory, before the police get here.”

In the big, wrecked room, the pale, all-seeing eyes dwelt briefly on the dead body of Robert Gant and on the wrecked apparatus. Then Benson strode swiftly to the one thing left untouched: the flat pan. He sniffed the colorless fluid in it.

It was plain water.

He looked at the little stack of glass strips beside the flat pan of water. In his pale, deadly eyes was a dawning glitter.

There was one other thing that roused that glitter. This, he found in the closet off the lab. And the object—or rather twin objects—was a pair of old shoes.

The soles were off the uppers, and the heels were off both. That was because there were no nails in the shoes. Each nail had been taken neatly from its hole, leaving only dissociated pieces of shoe leather.

It looked as though the killers who had wrecked the place might at the same time have stolen the nails from one of the Gant brothers’ shoes. But this made no sense at all!

Or—did it?

CHAPTER IV

The Sky Walker!

As temporary headquarters in Chicago, Benson had rented the entire top floor of a big hotel. Elevator operators had received orders to take no one to that floor who hadn’t phoned up first and gotten an O.K. That was because the underworld was beginning to realize the deadly enemy they had in the pale-eyed Avenger, and many were out to get him if they could.

Benson was up there now, talking to Josh Newton and Rosabel. Smitty and Nellie Gray and MacMurdie listened in.

“Then you have no idea what it was the brothers were working on?” Benson said to Josh.

“No, sir,” said the colored man. “I haven’t. Mr. Max and Mr. Robert kept their secrets to themselves.”

“You say their laboratory was broken into about a month ago, and something very important was taken?”

“Yes, sir.”

“And the brothers did not get in touch with the police?”

“No, sir. They didn’t want even the police to know what they were working on.”

“But Max Gant went to police headquarters yesterday evening.”

“Yes, sir. But that was because the pavilion had collapsed, and he was afraid there’d be more disasters if he didn’t tell what he knew—put the city authorities on their guard.”

“Then their inventions were definitely connected with that collapse, and with the noise in the sky,” Benson nodded. “But that’s all you know?”

“Absolutely all, sir.”

“The brothers must have had materials and supplies delivered. And I suppose you took them in occasionally. Can you remember what any of them were?”

“No, sir,” Josh said. But here Rosabel spoke up.

“I remember one thing,” she said. “It was a small package from the Warwick Corporation in New Jersey. I signed for it, and gave it to Mr. Max. He was too eager to wait till he got up to the laboratory with it, and opened it on the way up the stairs. I got a look at the stuff he took from the package. It was a thin, long strip of stuff that looked like glass. But I guess it wasn’t glass, because Mr. Max bent it around in his fingers. And he kept saying: ‘This would do the trick. As tough as steel and as transparent as glass.’ ”

Into Benson’s icy-pale eyes the glitter was coming.

“That strip,” he mused, “would be Glassite, a new Warwick product. It’s a plastic that is as clear as glass, but is unbreakable. Thank you very much, Rosabel. You’ve told me more than, perhaps, you realize.”

MacMurdie spoke, scowling. He was an expert chemist, and knew all about the new product, Glassite. But no perplexity had been cleared from his face by the mention of it here.

“What does all this rigamarole mean to ye, Muster Benson?” he asked.

“It means,” said Benson slowly, his dead white face like a mask of Fate, “that Chicago and the region around it will bitterly regret the day that strip of Glassite was delivered to the Gant brothers for experimentation. Now tell me, Josh, Rosabel, what are your plans for the future?”

Josh looked at his pretty wife. She nodded. The bond between these two was close enough so that looks could substitute for words.

“We could get another position pretty easily, sir,” Josh said respectfully. “Most of Mr. Robert’s and Mr. Max’s friends know about us and could use us. But we’d like to work for you if that’s possible.”

Benson’s unreadable, icy eyes probed the two of them.

Rosabel said: “Those two brothers were the finest men we’ve ever known. And they were murdered in cold blood. We’d like to work for you at least till those murderers have got what’s coming to them. We’ll work for nothing if you don’t feel you can afford us.”

Something almost like a smile touched Benson’s clear, pale eyes. Few people knew how much wealth he had acquired from previous adventuring. In addition, in southern Mexico in a cache known only to him and his associates, was the vast golden hoard of the Aztecs, buried centuries ago from the invading Spaniards, recently discovered by Benson through explorations of Nellie Gray’s archeologist father. That hoard was in Nellie’s name, but she had insisted it be used as an inexhaustible bank account by Benson in his crime work.

Asking if Benson could afford Josh and Rosabel was like asking if the United States mint could afford to hire a new scrubwoman.

“I’ll be glad to have you help us,” Benson said, after a moment. “But there may be danger—”

“We can take care of ourselves,” Josh said quietly. “What comes next?”

They all listened carefully for the answer to that. But Benson only shook his head and said:

“We’ll have to wait for the next break. We haven’t anything to work on at the moment. We know that some gang stole a secret invention—perhaps more than one—from the Gant brothers. We know that, thus armed, the gang has some huge, terroristic plot they’re working on. But—that’s all we do know. We’ll have to wait for the next development.”

The next break was not long in coming. It happened, not in Chicago, but fifty miles out along the lake past Gary, Indiana.

Up around the east side of Lake Michigan from South Chicago to the Catawbi Iron Range in Michigan, runs the Catawbi Railroad. It hugs the water edge, going through barren dune country for much of its length.

For freight, the Catawbi Railroad depends on shipments of ore from the Catawbi iron mines to the South Chicago and Gary, Indiana, steel mills. Passengers come from a score of pretty lake towns along the shore where commuters from Chicago live. The commuters board the Catawbi train, go to South Chicago, and there change to local transportation taking them to downtown offices.

This thing happened along the lake shore in a particularly deserted sand-dune region. It happened at a little after one o’clock in the afternoon. That was fortunate. At that hour, there were less people on the train to which it happened than there would have been during the commuters’ rush hour.

The five-car train of passenger coaches was rattling over the roadbed at a sixty-mile clip. The engineer was looking ahead all right, but not very attentively. There was no reason why he should be especially alert.

He had been over this stretch of right of way, in the other direction, two hours ago, and everything had been O.K. then. There were no crossings to watch out for. The day was clear and sunny, so vision was excellent.

He was looking, rather inattentively, at the roadbed ahead of the speeding engine. Then he jerked straight on the seat in the cab and stared with incredulous eyes. After that, he jammed on the brakes so hard the wheels locked and steel shrieked in anguish on steel.

Ahead, there was suddenly no railroad track to run on!

The track ran on for a few hundred yards more, then sort of melted away. Beyond that, as far as the bewildered eye could see, there were no rails at all.

The ties were there. Even at a moment crowded with horror, the engineer caught a glimpse of spikes in the ties in a line where rails should be. But there was no trace of the rails themselves!

At least two miles of track had vanished as though it had never existed—though it had been there two hours before.

The engineer was swearing in a cracked voice and jerking at the brake lever. The train was grinding along with locked wheels. And it hit the section where there were no rails to run on—

Heavy ties flew and splintered like so many matches. Sand rose in great geysers. The engineer and fireman had tried to jump at the last moment, but before they could the engine crashed over on its side. Broken boilers poured water on the hot fire, and there was a tremendous explosion.

The cars behind, with their hundreds of tons and mile-a-minute momentum, kept on grinding forward, pushing the debris of the engine along and piling in on each other. Then there was silence, punctuated by the crackle of flames and shattered finally by the screams of the passengers.

The conductor and brakeman, who had been in the last coach, were shaken up but otherwise unhurt. They rescued the passengers who were still alive, from the flames. The brakeman began running ahead to the next commuters’ town, over the roadbed from which the long section of rails had been so mysteriously taken.

The conductor raced toward a big man in ragged overalls who had helped in the wreck after appearing over the dunes a short time after the crash.

“Were you around here before the wreck?” the conductor demanded, almost out of his mind. It was the worst wreck in the road’s history. “Did you see anybody around here? Who could have taken a couple of miles of steel rails! And how, and why?”

The farmer blinked eyes that didn’t look very intelligent. He was shambling, shabby.

“I was around here for a coupla hours,” he said. “I didn’t see nobody anywheres near, though. Except in the sky.”

“In the sky?” chattered the conductor. “What are you talking about? What do you mean—in the sky?”

“I was around here lookin’ for a calf that got away,” the man said, blinking in stupid sympathy at the groaning forms laid on the sand. “I got a farm five miles in. I was in from the tracks a half-mile, mebbe. I heard a noise in the sky. It was like what a plane might make. Only there wasn’t no plane in the sky. But there was a man up there, walkin’.”

The conductor literally staggered. Then he cursed.

“Are you a lunatic? This is nothing to joke about. A man walking in the sky! You’d better have a better story to tell when the State police get here!”

“You asked what I seen,” the man said. “So I’m tellin’ you. I got good eyes. The best eyes of anybody in these parts. I see things most people have to have glasses to see. And I saw what I said.”

He shifted from one foot to the other in his earnestness.

“Way up in the sky, a guy was walkin’. Hunder’ yards to a step. He was pushin’ something in front of him. Looked about the size of a barrel. I don’t know what it was, and I don’t know how a guy can walk in the air, but that’s what this guy was doin’. I seen him plain, before he went into the sun and I couldn’t see no more.”

That was the man’s story, and he stuck to it.

He had heard a weird noise in the sky at about the time two miles of solid steel rails had vanished. He had looked for a plane, but had seen no plane. Instead, with a remarkably good pair of eyes, he had seen a man walking up there. Walking, in thin air! And pushing something ahead of him about the size of a barrel.

The crazy tale wasn’t worth paying attention to, of course. But, meanwhile, there was the theft of two miles of rail to clear up—and the thieves to be brought to justice for causing a railroad wreck of disastrous proportions.

The small Catawbi Railroad couldn’t stand many disasters like that wreck. In the small South Chicago office building owned as home office by the road, the president of the board of directors paced his office.

The president was Abel Darcey. He was not really a railroad man. He was a banker and a heavy investor in South Chicago industry, with a big home up along the lake.

The directors of the road weren’t railroad men, either. The Catawbi Railroad had a curious history.

Some years before, all the little shore towns through which the road had passed had decided that railroads were fair game for rich taxes. One after another, the townships had piled special taxes on the road till a point had been reached where its running was no longer profitable.

It had been abandoned. But that stranded several thousand well-to-do commuters with homes on the lake and offices in the city. So the commuters had gotten the taxes rescinded, each in the districts in which they lived; then they had formed their own stock company and taken the road over, with Abel Darcey to head the board of directors.

The road just about paid for itself, which was enough for the owners, since all they wanted was sure transportation. But there weren’t enough finances in its backing to stand shocks like that wreck!

Darcey stopped his pacing long enough to ring for his secretary. He was a clear-skinned man of sixty, with eyes ordinarily calm enough but now very worried indeed.

The secretary, a trim brunette, came in.

“Have you found out who made the offer to buy the road?” Darcey asked her.

“No, sir,” she said. “It came through the Michigan Bank. That’s all anyone knows.”

“Well, I notified all the chief stockholders that an offer had been made and they could get out from under if the wreck scared them off,” Darcey said, looking harassed. “I’m willing to sell and run. Got fifty thousand in the thing. Are the answers in yet?”

The secretary nodded. “One from Colonel Ringset, of Catawbi Iron Range, makes a majority report. I was just coming in with it. They don’t want to sell.”

Darcey sighed.

“I suppose they’re right in their attitude. But I wish I knew who wanted to buy. And I wish I knew what in Heaven’s name could be responsible for the disappearance of two miles—hundreds of tons—of steel railroad rails!”

The newspapers were out by then, with stories of the fantastic theft. All had big front-page headlines. But only one said anything about the sky walker.

A farmer had seen a man walking in the sky, taking hundred-yard strides and pushing something like a barrel ahead of him. The story was too silly for the big dailies to use. Only one, a minor tabloid, mentioned it.

CHAPTER V

Trapped!

Even without mention of the noise in the sky, Benson would have sped to the scene of the wreck with the first tick of the news teletype flashing news to the papers—and to him. The wreck was precisely the sort of thing he was half expecting as the next break.

But the tabloid’s account made him question the farmer first of all. The man repeated his account.

Benson’s pale eyes had no intimation of unbelief in them. Smitty and MacMurdie were looking askance at the man, but not Benson.

“You say the man was—walking—way up in the sky?” Benson said, paralyzed lips barely moving in his dead face.

“Uh-huh,” said the farmer.

“And he seemed to be pushing something ahead of him? Anyway—something was ahead of him?”

“That’s right.” The man grew belligerent. “Say, if you think I’m nutty, too—”

“I don’t think that,” said Benson quietly. “Now, you say he was walking very fast—taking huge strides up there.”

“It looked like he was takin’ a hunder’ yards to a step.”

“Mightn’t he, do you think, have been going even faster than that?”

“Yeah, he might. But he sure wasn’t goin’ any slower.”

They were standing near the wrecked cars. The roadbed, minus rails, was at one side of them. A few yards away, down a twenty-foot sand bluff, glittered the expanse of Lake Michigan, on the other side.

Several hundred yards out from shore a big lake steamer trailed a plume of smoke on its way toward Chicago.

“Can you,” said Benson, “read the name on that boat out there?”

The farmer stared out over the water for a minute, eyes narrowing.

“Sure!” he said. “She’s the City of Cleveland.”

Benson nodded. The name of the boat was correct, though few eyes could have been telescopic enough to make out the letters. Benson’s pale eyes could read them quite easily at that distance. It was obvious that this farmer had a rare pair of eyes almost as good.

And he had seen a man walking in the sky.

Benson and Smitty and MacMurdie left him and began walking up the railless roadbed. They left the wrecked cars, being cleared away by a work train, behind them. They entered a dune section where only the sand hills, like the rolling dunes of the Sahara, surrounded them. In a short time they were as cut off from the scene of tragedy, behind, and from any trace of human habitation, as though on an actual desert.

Benson examined the roadbed. His face, as ever, was as expressionless as a wax mask. But in his icily clear eyes was a look of surety, as if he knew in advance any story which might be told by the eerie disappearance of miles of solid steel. And in those coldly terrible eyes was death for the forces that had caused the disappearance of the rails.

The ties were there, on the roadbed. In them were the rusted spikes which had secured the rails. The rust on the spikes was absolutely undisturbed; there was no sign that they had been sledge-hammered over to get the rails up. In fact, there was no way under the sun in which those rails could have been taken.

Yet they weren’t there any more.

“There’s where they start again,” Smitty said, after nearly a half-hour of walking. He pointed along the roadbed. In the distance, the twin gleam of steel could be seen again. A little beyond that point there was a minor depot, of the sort that is locked and tenantless, save in rush hours.

“We’ll see what the ends of the rails look like,” Benson said, leading the way.

He seemed to flow along the rough ties—not a big man, weighing only around a hundred and sixty-five pounds—but possessed of some mysterious quality of muscle that far outmatched in power sheer quantity. The giant Smitty moved lightly behind him, for all his bulk. And last trailed MacMurdie, with the bleak fighting gleam in his bitter blue eyes at the thought of the broken bodies behind them.

They got to the place where the rails resumed their ruler course. Here, the rails ended bluntly. There was no fading or melting off into nothingness. There were no rails, then there were rails, with the rail ends square and untouched.

A little beyond, several rails were missing, but beyond that, again, they were whole.

Benson stooped and looked at the rail end.

“I’d like a piece of this to have analyzed, Smitty,” he said.

The giant bent down. The rails were old; had been in use a long time. Countless car wheels pounding over them had flattened them a little and forced the steel out in ragged little scallops at the edges. It is a formation to be found on most old rails.

Smitty put gigantic thumb and forefinger on one of the thin splinters, twisted hard, straightened up. He handed the fragment to Benson, who put it carefully in his pocket.

The gray fox of a man had ears as miraculous as his eyes, and so he heard the sound first. But Mac and Smitty heard it, too, very shortly after that.

The sound in the sky.

From somewhere overhead could suddenly be heard a faint, monotonous drone. The three of them searched the sky with their eyes for the sight of a plane. The noise was much like that which a plane motor might make.

They couldn’t see anything up there!

It was about five o’clock by now, and the western sky was a red glare. Even Benson could not have seen if a man were “walking,” if he happened to be in the western heavens.

Thus, none of the three saw anything. But all of them heard the droning noise. It seemed very far up, very far away. It went on and on while they stood there craning their necks.

Smitty saw the next thing first. He was peering in all directions, and he happened to stare down the railroad track near the horizon.

“Look!” he said, clutching Mac’s ropelike arm with one hand and pointing with the other.

He was pointing and staring with stupefied eyes at the little depot down the line.

The depot was an old building, about as big as a six-room house. It had been built in the era of gingerbread architecture. There was a silly little cupola on it, which served no purpose. The rest of the frame structure was bare and unadorned, squatting like a crate beside a wooden platform bordering the track.

The cupola was the first to go. It was leaning drunkenly when Smitty exclaimed aloud. After his cry, it seemed to melt, like a big cube of sugar. And under it the building began to dissolve, too.

It was not quite a collapse; not like the account they had read of the pavilion in Lincoln Park. The thing just fell slowly, almost gracefully, to pieces, and it finally ended in an unsightly stack of old boards, beams, and slate shingles. There hadn’t even been much noise connected with it; just a low rumble like that of a colossus muttering in his sleep.

They ran toward it.

The noise in the sky was fading out, toward the west, over the open lake. It was gone by the time they reached the collapsed depot.

They searched swiftly in the wreckage for people, with Smitty hauling beams and timbers with the strength of a bull elephant. They soon discovered there had been no one inside. Then they began to look around.

Benson seemed to be hunting for something specific. Board after board he picked up and searched carefully. He sighted along each, looked at the ends of each, his pale eyes taking on a look of microscopic concentration.

“So that’s it,” Smitty heard him whisper to himself, dead lips barely moving in his dead face. But what “it” was, Smitty could not imagine.

There was a puffing in the distance. They stared that way.

Along the whole trackage, beside the shimmering lake, a work train was coming to help clear the wreckage down the line. There was a small and rather ancient switch engine, followed by two flatcars loaded with rails with which to start rebuilding the track, and ending in an ancient day coach for the repair crew.

The three-car train stopped at the collapsed station. It would have had to stop anyway, because part of the melting structure had spilled out over the rails and blocked the way. But the manner in which a man leaped from the rear car and strode toward Benson and his two aides told that the train would have stopped anyhow, at sight of them, to investigate.

The man had a gun in his hand, which was leveled at him. He was hard-jawed, broad-shouldered, with a battered felt hat. His whole appearance spelled track foreman.

“All right, you guys,” he bellowed, as he neared them. “Who are you? What’s the idea, blowing up this station? I guess the three of you’d better come along with us for some fancy questioning.”

More men were pouring from the old day coach, behind. They came threateningly toward the three. Some had guns, some had ax handles, some were armed with crowbars.

Smitty hunched his huge shoulders warily. The situation looked tense. He could handle any four average men, but there were sixteen or eighteen in this railroad mob. Those were odds too great even for him.

“I’m investigating the loss of the rails, back up the line, and also the destruction of this depot,” Benson said quietly. “I have credentials, if you’d care to see them.”

The man with the battered hat calmed down a little.

“Hand ’em over,” he grunted.

Benson did so. There was a letter from Chicago’s police commissioner to whom it might concern, and one from the governor of New York State.

The man read slowly, carefully, and as he did so, the rest crowded close. It all looked very natural and innocent. It was so smoothly done, that no one could have guessed the transformation that was to come.

The man who looked like a foreman handed the credentials back to Benson and pocketed his gun.

“I guess you’re O.K.,” he said.

At that moment, with the three men completely off guard so that they could not possibly have drawn weapons in time, the railroad crew became a mob of killers.

Into the hand of each leaped an automatic; all of them were leveled at Benson and Smitty and Mac. The ax handles and crowbars had been only so much stage setting; now they were shifted to left hands while rights held guns.

“So you’re investigating these things,” the mob leader mimicked Benson. “Well, you won’t investigate any more. Into that last car, you guys.”

Benson stood still, with his deadly, pale eyes raking over the men. They shifted uneasily under that icy gaze. They were six to one, and had guns; but something in this man’s colorless stare made them nervous.

“Maybe we better bump ’em now and have it over with,” one of the mob mumbled.

The leader heard and shook his head.

“No! We follow orders. A slug in the skull shows right away something besides an accident happened. And this has to look like an accident. Go on! Go on, get into the end car.”

Benson and Smitty and Mac let themselves be prodded up the steps of the end car. Their capturers crowded in after them.

The man who had played the role of foreman stared at the captives.

“You look like three tough guys, all right,” he said. “I can see why you got to be knocked off.”

They tied the three securely to the old plush seats of the day coach, using one-inch rope from a big coil in the forward tool locker. They were wary of Mac because of the way his bitter blue eyes burned at them. They moved gingerly around Smitty, awed by his huge size. But they were most careful of all with Benson.

Something in the pale, deadly eyes, calm and cold in the white deadness of his immobile face, gave them all the shivers. Five covered him with automatics while the sixth passed loop after loop of rope around his compact body.

Then it was done. In three seats, one behind the other, Benson and Mac and Smitty sat upright with enough rope around each to bind half a dozen men to the seat backs.

The leader of the murderous crew waved an arm out a window. There was a hiss from the switch engine; then it started backing slowly in the direction from which it had come.

“Johnny,” the leader said to one of the younger men, “run up to the engine and tell Clay to slow down at the bend where we left the automobiles. We’ll all jump off. Then tell him to lash the throttle full open and jump himself.”

The man went back toward the engine. Mac saw him swing out the door and weave over the rail-piled flatcars. The gang leader grinned at Benson.

“Like an accident, we’re supposed to make this. So like an accident it’ll be. There’s a sharp curve eight miles up. So sharp that any big-time railroad would have straightened it years ago. The work train will hit it at about seventy an hour, and I guess it’ll go straight instead of around the bend.”

Benson said steadily: “The train crew you overpowered to get this train can testify that a wreck at the curve was no accident.”

The man grinned again. It was a forced grin, however. Obviously, he was anxious to get out of sight of The Avenger’s pallid and deadly eyes and death-white face.

“We didn’t knock out any train crew. These cars and the engine, with steam up, were at the next town with nobody on it. Everybody was gettin’ orders, I guess. So we just borrowed it. The verdict’ll be that you nosey investigators took it for some cockeyed reason, didn’t know how to run an engine, and wrecked yourselves.”

There was a brief toot from the engine in the rear, and the cars began to slow. They swung around a bend. Looking out the window, Benson saw four or five automobiles on a dunes road waiting to pick up the men.

“So long,” waved the mob boss. He went to the door and dropped from the train. The others followed.

There was a sudden jerk from the rear, and the engine roared as its drivers spun on the tracks. The throttle had been jammed wide open, and the driving wheels wouldn’t take the load without slipping, at first.

The three-car train rolled down the track, jerking as the spinning wheels caught for a moment, easing off as they slipped again. Benson saw a last pair of men scrambling into the automobiles on the lonely lane. They had acted as fireman and engineer. The roaring locomotive behind them, full throttle, was empty now.

The rail joints began clicking under them at a swiftly increasing rhythm as the driving wheels slowly stopped spinning and began to make each stroke of the racing pistons count.

Benson sat straight in his seat, bound tightly, with Smitty ahead of him and MacMurdie behind him. Behind the dead-white face of the Avenger burned the discovery he had made in the debris of the wrecked depot. A discovery it looked as if he might never follow up, now.

The discovery that in all that pile of old boards and rubble there had been not one screw or nail. All had gone, as though someone, hours before, had removed each with painstaking care, leaving the building to fall like a house of cards the moment a breeze struck the unsecured beams and boards.

CHAPTER VI

Trickery Succeeds!

If one of the more dignified Chicago newspapers had come out with the headlines, the city might have paid more attention to them. But they appeared only in a sensational sheet whose owner was notorious for getting news scoops by the simple process of making up his news as he went along.

Because of that, most people smiled at the screaming headlines. But under the smile there was uneasiness, too. After all, a pavilion at the south end of Lincoln Park had collapsed.

IS WAR DECLARED ON THE

UNITED STATES?

That was the idiotic headline in the sensation sheet. The account went on even more idiotically.

It seemed, according to the correspondent who had gotten his news from a source that “cannot be divulged,” that an unnamed foreign power was going to hold up the United States for some vast bit of international booty, as yet unspecified. Perhaps for the rich province of Alaska. Perhaps the demand would even include the Western coast with the States of Oregon, Washington, and California.

This unnamed enemy was going to invade the interior of the United States. Chicago and vicinity, to be precise. The enemy claimed to be able to destroy at will, with no man able to learn the source of the destruction. There would be no way of fighting back; the country would have to give up whatever territory was demanded, or see its rich inland cities turned into collapsing charnel houses.

The managing editor of the Chicago Record studied his rival’s scoop and finally relaxed.

“Hooey!” he said. “No enemy nation can strike unseen. And if one could strike, the East coast would be the target, not the Middle West. The intimation is that the Lincoln Park pavilion was a sample of the destruction. But we all know that the reason for that collapse was structural failure of the girders. The steel corporation sold the city bum goods, that’s all.”

The city editor agreed with him. It was good policy, of course, to agree with him; but in this case the city editor could nod wholeheartedly.

“For thirty years that rag has pulled a phony war scare every so often to jack up its circulation. It’s just doing the old trick again.”

Up in the Avenger’s temporary headquarters, Nellie Gray and Josh and Rosabel Newton studied the sensational headlines.

“I wish Mr. Benson were here,” Nellie said, her pink-and-white face twisted with worry. “An enemy invasion? It doesn’t sound right. But he could probably read a meaning in the account that no one else could.”

“He’s a great man,” said Josh. White-jacketed as a standard servant would be, he was now moving at his normal pace—which was very slow. And his thin, dark face had taken on the deceptive, somnolent look that had caused him to be nicknamed Sleepy.

“You feel, when you’re near him, like you feel in a powerhouse, standing next to a dynamo,” nodded Rosabel.

“I’m almost afraid of him,” Josh mused. “Yet I’d do about anything he asked me to do.”

“He’ll never ask you to do anything unreasonable or that he wouldn’t try himself,” Nellie said. “You can depend on that—”

There was a buzz of the telephone. She picked up the receiver. On her lovely face was a look of extreme wariness.

Dick Benson interested himself only in cases beyond the powers of the police to handle. Such cases necessarily meant that men were involved who were far more intelligent than the usual criminal. And such men were quick to find out precisely who was fighting them so efficiently—and to try with every sinister means at their command to wipe out The Avenger and his helpers before they, themselves, were wiped out.

Every ring at phone or doorbell might be the preliminary to some murder attempt.

This ring seemed all right, however.

“A Mr. Carlisle to speak to Miss Gray,” came the voice of the hotel’s switchboard operator. “Concerning Mr. Benson,” she added.

Then the voice of the man in question.

“Miss Gray?” He spoke urgently, hurriedly. “May I come up for a moment? I have an important message for you, from Mr. Benson. Or, if you like, you can come down to the lobby.”

Nellie decided on the first suggestion.

“Come up, please.”

The elevator boys, drilled by Smitty, had a code when they stopped at this top floor occupied only by Benson and his associates. When they brought someone up, they were to clang the door for every passenger in the car. They were to stop the cage just a bit off line, start to open the door, clang it shut and send the cage up or down a fraction to correct the mistake. It was easy and unsuspicious. One clang for a single visitor, two for a couple, three for more than that.

Nellie heard the door clang only once. Then there were quick steps, and a tap at their door. Josh opened it. He had slid into his role of a sleepy, harmless Negro.

“Yas, suh?” he said inquiringly.

“To see Miss Gray,” came a man’s voice. Then the man stepped in.

He was young and well dressed and blond. He looked like a bank teller or some such person. He turned quickly to Nellie Gray, hat in hand.

“I’m John Carlisle, private secretary to the superintendent of the Catawbi Railroad,” he said. “I was sent here by Mr. Benson, with orders to come and get you and a certain chemical he wants, and return as soon as possible. He is out along the roadbed and needs it.”

“The chemical?” Nellie asked.

“Some concentrated sulphuric acid. He wants to make a rough analysis of the track steel. You’re to come, too, because he intends to stay in the town of Rosemont, nearby, overnight, and has work for all of you in the early morning.”

Wherever Benson went, three large trunks went with him. In the trunks, which were miracles of compactness, were racks of chemicals and of delicate apparatus. It was a complete traveling laboratory.

Nellie Gray hurried to one of the opened trunks and got a vial of the super-sulphuric mentioned by the man. It was deadly, terribly stuff, this concentrated acid.

She glanced at Josh in indecision. His quick intelligence caught her unspoken question.

“If Mistah Benson wants ever-body to be on hand early in the mohnin’,” Josh said sleepily, “mebbe me an’ mah wife oughta come ’long with Miss Gray.”

Carlisle shook his head. “Mr. Benson said you were to stay and take any phone calls that might come.”

“But if he wants all of us—”

Carlisle seemed unconcerned.

“I’ll leave that up to you. Mr. Benson said for you to stay. But if you feel you should join him, that, of course, is your lookout. I’m not familiar with his methods.”

“You’d better stay, Josh,” Nellie said. She was hurriedly putting on a poker chip of a hat and thrusting the little vial of concentrated sulphuric acid into her purse.

She caught up the sensational newspaper on the way out. At the elevator, she showed it to the man.

“Has Mr. Benson seen this, do you know?” she said.

Carlisle shrugged.

“I don’t know. But I wouldn’t put much stock in it, myself. An enemy invasion! It seems pretty ridiculous.”

They went down through the crowded lobby and to the street. Carlisle’s sedan was near the door. It was black, streaked with the dust of the dune region.

“We’ll go by car to South Chicago and by speedboat from there,” Carlisle said. “That’s the fastest way. Will you sit in the back, Miss Gray?”

Nellie nodded, and got into the rear of the car. Carlisle slid under the wheel, and the sedan began humming south over the boulevards. They got out to South Chicago in short order, and turned toward the lake.

And suddenly Nellie felt herself growing overpoweringly sleepy!

It was such a natural feeling of drowsiness that for a few seconds she didn’t question it. But after that, she felt wild alarm flood through her. Something was the matter! Something was happening!

She tried to get up, and couldn’t. She fumbled weakly for the handle of the rear window, but her fingers fell from it after a bare touch.

She saw that Carlisle, at the wheel, had the lapel of his coat up and that his head was twisted sideways. He was breathing through the lapel. Probably the fabric had been chemically treated to counteract whatever fumes were making her so sleepy.

She saw the lake, at the street end ahead. And then she slumped against the side of the car with her sleek gold hair against the window.

But Nellie Gray wasn’t quite out.

The rear windows of the sedan were of the type which slide backward an inch, with a turn of the handle, and then lower.

Her one touch at the window handle had slid the glass back a quarter of an inch or so. And when she slumped, she managed to do so in a manner that brought her pert nose to this crack.

So she was not quite unconscious when the car stopped at a small, rickety dock, but she might as well have been, for the fumes had made her too weak to put up a fight.

At the dock there was a motor cruiser almost large enough to be called a yacht. Two men were on deck. They grinned at Carlisle as he opened the car door. They were hard-looking customers, but in Carlisle’s smooth face was now a look harder even than theirs.

“Got her, huh?” said one of the men as Carlisle picked Nellie up and carried her to the cruiser. The speaker caught the girl rough by the arms and dragged her over the rail and aboard. “Good going! Now we’ve got ’em all in a bag.”

Carlisle went back to the sedan.

“See you at the ferry,” he said. “So long.”

The sedan moved off and the boat moved out. It was getting along toward dusk. One of the men lit the boat’s riding lights. The other stepped to where Nellie lay.

She was drawing in lungfuls of fresh air, and was snapping out of it rapidly. But not rapidly enough! She still hadn’t the strength to put up a battle.

The man picked her up like a sack of meal and took her below. She felt herself dropped into darkness. Forward, she heard the loud roar of the marine motor and knew she was very close to it. Under her, right next to her ear, it seemed, she heard the rush of water as the boat forced itself ahead at thirty miles an hour.

Over her, the last crack of light went out as a stout hatch was closed. She was held in the tiny hold of the cruiser, caught as securely as any prisoner behind bars in a penitentiary.

Carlisle’s demand for her to bring a chemical to Benson had been just natural enough for her to be caught off guard. And it looked as if she were going to pay bitterly for that.

CHAPTER VII

Death—Odds-On Favorite!

Fergus MacMurdie had a most peculiar trait. When everything was going smoothly, it was his dour Scotch nature to predict the most dreadful things that were sure to happen any minute. Always he looked on the gloomy side of life.

But when an emergency arose in which these seemed no conceivable way out, he grew almost cheerful, and predicted sure success.

On the work train, Smitty’s gigantic muscles were writhing and straining against his bonds as he stared out the window. Free, and with a good purchase for back and arms and shoulders, he might possibly have broken the rope. But in his cramped position a solid inch of good new hemp was a good deal too much, even for him.

“We’re sunk,” he said, looking out the window at the scenery flashing past. “Those guys said we’d hit seventy. My guess is we’re topping even that speed. And when we hit that sharp curve—”

“Whoosh, mon,” said Mac, straining at his own ropes, “we’ll come out of this. We’ve come out of worse.”

“You’re nothing but a disgusting Pollyanna,” snapped Smitty.

“And ye’re just an overgrown schoolboy who gives up at the first lick of teacher’s ruler on the back of yer hand,” burred Mac.

“Oh, I am, am I!” In his indignation, Smitty almost broke free.

Behind them the overstrained switch engine roared like a tortured bull, with its drive wheels turning so fast they were mere blurs. And Smitty thought of something else. Something adding no cheer whatever to the scene.

“Those two flatcars loaded with rails!” he said suddenly.

“What about ’em?” said Mac.

“When we go off the track, the car we’re in will bury itself and stop—but the rails on those flatcars won’t! They’ll break their chains and keep right on sliding forward. Two carloads of steel rails. They’ll spill all the way through this old wooden day coach like a couple of hundred half-ton lances.”

Smitty began fighting his bonds with renewed fury. And then Benson’s quiet voice sounded over the uproar of the speeding work train.

“Mac, are your legs free?”

“Yes, they’re free.”

“Then,” said Benson, “put your feet against the back of my seat, if you can, and push me as far forward toward Smitty’s seat as you’re able.”

They were seated in line, first Smitty, then Benson, then MacMurdie. The gang had bound them to the backs of the three seats, but hadn’t bothered with their legs. Why should they? A man can’t untie himself with his feet.

But the gang had neglected to search the three from the knees down, as well as up, for weapons. Which proved that they were quite unfamiliar with at least one of The Avenger’s armament habits.

Benson habitually wore, in a slim holster strapped to his right calf, the small, special, silenced .22 pistol which he called, with grim affection, Mike. Strapped to the other calf was a needle-like throwing knife with a light, hollow tube for a handle, which was designated Ike.

Now, the man with the white, dead face and the death pools of eyes had managed to draw his left leg up enough to get the handle of razor-sharp Ike in his fingers.

Benson couldn’t cut himself free—he hadn’t that much leeway of motion. But he could cut the giant Smitty loose if he could lean forward enough to reach the ropes where they wound around the back of Smitty’s seat.

And the seats of the day coach were standard, in that they could be tilted forward to reverse the seating arrangement when the end of a run had been reached.

Mac put his huge feet against the back of Benson’s seat and shoved. Benson and seat back and ropes all shifted forward. Ike’s sharp edge almost touched Smitty’s lashings.

“More,” said Benson.

The Scot shoved harder. Benson drew his lithe body in on itself at the waist, and the knife touched.

The blade had bitten only half through the key loop when Smitty’s giant muscles suddenly completed the task by snapping the rest. He burst free and stood up.

A powerful thrust freed Benson, and another did for MacMurdie. Then the three stared out the front door of the car in the direction in which they were speeding, and Smitty’s great hands clenched.

The work train was almost on the curve the gang leader had mockingly mentioned.

The roadbed hugged the lake shore here as it did in most of its length. The water was about twenty feet down, over a sand bluff which formed a natural breakwater to keep the track from being washed out during storms.

A little ahead, the track curved sharp right, to follow a similar curve of the beach. And the work train, roaring over the rails, could not possibly make that turn. It would plow straight ahead, over the twenty-foot drop and into the. lake.

“Whoosh!” cried Mac. “We’ll have to jump—”

But a leap from the train at that great speed would be as deadly as staying on it and being plunged on and on into the lake.

They couldn’t jump off and they couldn’t stay on.

It is the main characteristic of great leaders that in times of catastrophe, other men, who might be brilliant and capable themselves, look to them for direction.

Mac and Smitty looked at their ice-eyed chief that way now. And without faltering Benson answered. His face, unable to change expression even at such a time of crisis as this, was a fearful, dead mask. His eyes were like cold gray flames. But his voice was quite calm.

“Top of the car. Fast! At the last moment, jump to the side as far as possible.”

Mac and Smitty leaped to obey even though, for a few seconds, the meaning behind the strategy didn’t become clear to them. At the open door of the speeding car, Smitty caught Mac by the thighs and lifted him straight up till the Scot could grasp the shank of the old hand-brake wheel atop the car. The shrieking rush of air caused by the train’s speed helped hold Mac in place.

Smitty tossed Benson up the same way, then swarmed up himself like a great gorilla. For just an instant his eyes rested speculatively on the hand brake, but he knew the thing had no meaning here. He could twist it clear off, and the speed of the train wouldn’t be slowed enough, in the short distance left to the curve, even to notice.

“Here we go!” his great voice loomed.

The roar of the locomotive behind them had risen to a steady shriek. The flatcars loaded with rails were doing a kind of devil’s dance along the track, seeming almost to leave it at times, such was the pace.

They had almost reached the sharp curve ahead!

Benson was crouching on the sloping left side of the car roof, the lake side. Smitty and Mac had taken similar positions, several yards apart.

They swayed there on the balls of their feet, on the lake side of the jerking car. Benson hadn’t had to simplify his orders any more. Their quick brains had understood when they were on the car top.

The old day coach hit the beginning of the curve. With its first awful lurch, Benson and Smitty and Mac jumped.

Like three stones shot from a sling, their three bodies whirled out, away from the track, over the twenty-foot drop, a dozen feet out into the lake. The terrible snap of the car at the curve, plus their own impetus, had catapulted them an unbelievable distance.

They hit—not hard earth as they would have struck had they leaped before—but waist-deep water. Hitting even this, with such force, was a little like being rolled over granite paving blocks. But at least it wasn’t sure death.

They plowed like surfboards over the water for a dozen yards, then sank, but came to the surface again in time—so short had been the elapsed interval—to see the last of the work train.

For an instant it had seemed that the three cars and the engine would actually make the curve, in spite of the terrible speed. But the instant hadn’t endured. Halfway around, the old day coach tore from its forward truck and launched out over the embankment into the lake. The three flatcars and the locomotive followed it, like obedient sheep following a leader’s change of course, while the loose truck and car wheels went skimming on end around the curve and off down the track.

The coach struck the water with a geyser splash like the eruption of Old Faithful. It kept on going.

On the flatcars behind, the chains holding the tons of rails did queer, snaky things, and the rails began to cascade forward, driven by their original impetus.

The rails went into the rear end of the wooden coach, and on through and out the front end, like giant needles piercing through tissue paper. And behind them came the engine. Hundreds of tons of train, going at well over a mile a minute, takes a lot of stopping.

The day coach was shoved out till it was clear under water before the forward movement ceased. By then it was so pierced by rails that it looked like a giant’s pincushion. And then the water hit the locomotive’s firebox—and that was that. The whole west beach of Lake Michigan seemed to rise up into the air, spit out rails and sand and pieces of car wheels. And then there was silence.

Mac stood up in water about breast-high and wiggled both arms. They seemed to work all right. He moved his neck and legs. He was apparently unfractured anywhere; and Smitty and Benson seemed that way, too. It had been a narrow squeak indeed, but now all seemed clear sailing. Whereupon, the Scot instantly began to view the world with gloomy pessimism.

Even his pessimism was put to it to function after such an escape. But finally he found something to croak about.

“Whoosh!” he said, wringing at his wet coat sleeves and scowling bleakly. “We’re through now. Ye know, we’ll catch our death of colds in this water if we don’t watch out.”

Benson had the map of the railroad’s course in his mind.

“Rosemont is about five miles up,” he said. “It’s one of the bigger shore towns. We can get a car there—maybe a plane.”

But they weren’t to get to Rosemont without a short delay.

They saw the great dark bulk of the shore when they’d rounded a headland about a mile up. A huge thing like a long, flat box with the ends undercut, weather-beaten and shabby.

It was a car ferry. On the sides were still the letters, “Catawbi Railroad.” It was high on the beach, but such was its length that the far end extended quite a distance out into the water. Its condition suggested that it had long outlived its usefulness, and hence had simply been beached and abandoned. So there the great scow stood, like a tremendous cake of soap half in and half out of the lake.

Benson’s icy, pale eyes probed the vast hulk as they approached it. When they were even with it, Smitty and Mac started to swing on, but Benson stopped them.

“I think we’ll have a look at that,” he said.

They covered the hundred yards from track to water, and walked around the part on the beach.

At end and sides, the heavy timbers rose like an unbroken cliff, offering no way into the thing. It was just what it seemed, an abandoned barge on the beach. But Benson still was not satisfied. The opposite end, out in the lake, was out of sight of anyone standing at any point on the shore.

“We’ll wade out,” he said.

They waded, then swam. And Benson’s thoroughness was justified. In the lake end of the ferry, which loomed up at least twenty feet from the water, was a thin crack which ran on and on till the eye took in the fact that it was the edge of a gigantic door.

A portal taking up almost the whole end.

Down at the side, near the water, a plank was broken in what seemed an innocent way. But as they swam nearer they saw that the jagged resulting hole was ample to take a man’s body.

The broken plank made a little door beside the huge one.

The three went in, with Smitty having a little trouble forcing his great bulk in the small opening. Inside, the feeling was that which you get in a big cave. All was darkness; the fragment of light coming in where the plank was broken away did not extend for more than a few yards.

Benson took out a small flash whose case was waterproof and whose bulb had withstood the shock of hitting the water. He played it around.

The tiny ray didn’t begin to penetrate the length and breadth of the ferry. But it did light on something that brought instant identification to all three men.

That object was a length of small, narrow-gauge track running at a slope down into the water at the lake end of the ferry. On the track was a small wooden cradle mounted on flanged wheels. It was the sort of runway which is used to haul surfboats out of the water and up on a drydock.

Or amphibian planes.

“This may have been abandoned once,” said Smitty. “But it isn’t any more. It’s being used as an airplane hangar now.”

“For once, ye’re right,” said the Scot. Between him and the giant had developed a habit of biting repartee that might have made a stranger think they disliked each other very much. But the stranger would have been wrong.

Benson eyed the track with thoughtful, pale eyes. In the icy clarity of those eyes was grim urgency. Many lives had been lost in the affair of the man who walked the sky. Every fiber of the dynamic body impelled Benson to fast action lest many more be lost.

“I’ve got to get back to the city,” he said, dead lips, as usual, barely moving in his paralyzed face. “But just the same, this place ought to be investigated thoroughly. Smitty, you look around and come back to me with a complete report. Mac, you’d better come with me.”

The gray fox of a man went out the broken-plank exit, followed by Mac. Smitty was left alone in the vast interior of the barge.

When the human dynamo, whom men called The Avenger, had gone, it seemed as if a light had been turned out in the place, leaving it darker than before.

CHAPTER VIII

Cold Extra!

In Chicago, people were still chuckling over the sensational newspaper’s foreign-invasion hoax. An unnamed enemy ready secretly to invade the United States in the vicinity of Chicago? Hooey!

In a lunchroom downtown, several men were laughing about it to the proprietor. One, a big fellow with a gold front tooth, gesticulated.

“I guess if anybody did invade this country, it wouldn’t be secret. And I guess we’d know in advance who the enemy’d be. Besides, how could anybody invade us, and us not know it until after the damage was done?”

“Well, there was that pavilion in Lincoln Park,” the other man said. “Kind of funny how that fell down.”

“Aw, it didn’t have anything to do with an enemy invasion. The girders were rotten, that’s all. The city engineers said so.”

“The whole business is nutty,” said the proprietor of the lunchroom. “Wonder where the paper got that crazy story, anyhow?”

Someone else was wondering that. And that person was a lithe, powerful figure of a man with icily flaming gray eyes. The Avenger.

Benson was in the office of the managing editor of the sensational sheet now. Benson, who knew an amazing number of people in all walks of life, was acquainted with the owner of the paper. The owner didn’t like Benson much, but he was afraid of the pale-eyed man. And when Benson had quietly demanded authority to question the reporter of the paper who was responsible for the invasion yarn, the owner granted it.

Benson was probing the fellow now.

The reporter, a not-too-clean man of forty-five or so, stood like an uneasy schoolboy before Benson in the managing editor’s office.

“Your superior,” Benson said quietly, “disclaims all knowledge of the source of that story. He says it isn’t up to him to question news sources. He gets stories from his reporters, and passes them if they look interesting. He got this yarn from you, decided it would sell out the issue, and printed it. But he insists he doesn’t know where you got hold of it.”

“That’s right,” said the managing editor quickly.

“So now you can tell me where you picked it up,” said Benson.

“It was a source of information that can’t be divulged,” the reporter began, sweating under the gaze of the icy, pale eyes.

“It will be divulged in this case,” Benson said. The reporter knew that the dead-white face, with its awesome lack of expression, was going to follow him around in nightmares.

“I . . . I don’t know the name of the m-man who told me,” he stuttered.

“You don’t know the name of the man who gave you a story like that?”

“No! I got it in a bar, from this guy—”

The managing editor broke in, voice weary and daunted.

“This man”—he jerked his head toward Benson—“seems to be a buddy with everybody from the President of the United States down. Apparently he can call out the United States army if he wants to. Open up!”

The reporter cleared his throat.

“I really did get the story from a guy in a bar,” he said. “But I have an idea the man was there because I usually hit that bar at that hour, and he knew it. He was a young fellow, smooth-looking. Said his name was Carlisle. He spilled the foreign-invasion stuff, and it sounded like a circulation getter to me.”

Benson’s eyes, cold as ice in a polar sea, went from the reporter to his boss.

“All right! You got the story. It sounded like a circulation getter. But you wouldn’t have printed a thing like that without some sort of confirmation. What was it?”

The office door opened under the careless hand of a man from the shop in the basement. Equally indifferent to visitors in the boss’s office, the man came forward with business that usually took precedence over everything else. Proofs of the next edition.

“Get out of here!” squalled the managing editor. “I’m busy! Can’t you see that?”

“But—” began the man, in wonder. “These gotta be back down right away or—”

“Beat it, I said! And take that stuff with you!”

But the boss was a little too late. Benson’s hand, with its long, steely fingers, was out in an imperative gesture. The pressman found himself handing over the proof sheets without quite knowing why.

Both the reporter and the editor tried to grab them from Benson’s hand. But he had already read the screaming headline:

LOOP BUILDING FALLS!

Benson snatched up a phone and got headquarters. He turned from a few brief words, and his eyes were flames as they flared at the editor.

“No Loop building has fallen, yet. But you get out this extra! That means that you have reason to believe a skyscraper will fall very soon. About the time this paper can get to the streets. What reason have you to believe such a thing?”

Both were still, like frightened animals in the face of the glare from the deadly, colorless eyes. Benson’s hand went out. It got the reporter’s collar. He hauled the man to him as if he had been a child, though the reporter was a bigger man.

“Tell me—or be indicted for murder that you might have prevented! For if a building falls—with your knowledge of it in advance—people will die.”

“There was nothing I could do!” bleated the reporter. “The guy told me a building would fall at about six thirty, to prove his story.” He straightened, and there was a certain dignity about him for a moment. He worked for a paper that was a bad smell among news mediums, but there were things he would not do.

“I was going to turn him over to the cops,” he said. “I swear it! But I guess he’d figured that out in advance. Anyhow, he belted me one with a sap or something. Knocked me out. When I came to, he was gone. Look.”

He pushed back hat and hair and showed a livid blue bruise above his right temple.

“What was I to do after that? If I told the cops, all the papers in town would have the story in ten minutes from the police blotter, and there’d go my scoop. Anyhow, the cops won’t be able to do anything, because the attack is coming from the air.”

“So you did nothing,” Benson said, voice brittle.

Again, for an instant, the reporter was not without dignity.

“I got in touch with Fort Sheridan. At any minute now, all the planes up there will be in the air, to circle over Chicago all night, if necessary, and keep the thing from happening—”

“They won’t be able to prevent it—as you’re very sure right now, or you wouldn’t have gotten out this extra,” Benson said. “Turn every effort to tracking down the man who calls himself Carlisle. Understand? Report to me at the Wheeler Hotel.”

He went out, not seeming to exert himself but moving with a speed that strained the eye to keep up with it.

Benson went to the hotel, to his topfloor headquarters. And there he learned for the first time that Nellie Gray had gone out with a man named Carlisle. Mac, who had come to the hotel before Benson, had already heard and was wild with anxiety.

Benson heard from Josh of the ruse that had been pulled. He, Benson, had supposedly sent word for her to bring concentrated sulphuric acid to the railroad station, so he could conduct a rough test on a rail. It was a simple, clever story that might have taken anyone in.

But Benson dared not take time to try to find her now.

“Mac,” he said, “go to the yacht club and get the plane from her moorings. Have her warmed up and ready for instant use.”

Mac went out. Benson took from one of the trunks, that formed a compact traveling laboratory, a small but beautifully complete recording device, equipped with radio amplifier, that would have amazed any of the big electrical-research laboratories.

The Avenger believed implicitly in the terrible prediction that a Loop skyscraper was to fall. He believed it would occur at about the specified hour, six thirty. It was now twenty after. In the ten minutes remaining time, it would be impossible to set a guard on every tall building in Chicago’s downtown section, or to find out what building was doomed.

Benson could do things beyond the powers of ordinary men. But even Benson could do nothing, now, to save the structure, whichever it might be.

But he might learn something vital from the impending tragedy.

He opened one of the windows wide, and set the recording device on the broad sill. He put on a soft-wax disk, and started it going. The disk wore itself out with nothing to record, but he had barely got the second in place when the sound commenced.

A faint, monotonous droning in the sky, like the noise of an airplane motor, but with an angrier, shriller snarl. You’d have sworn there was a plane up there.

But you could look your eyes out in the clear dusk and still not see a plane.

The noise from the sky grew louder, settled on one penetrating pitch. The recording plate steadily picked up the tone. And beside it, the cold-eyed man stared into the high heavens with eyes like ice pools in hell as he imagined the thing that must be happening not far away.

For just an instant his telescopic, colorless eyes picked up something. A little dot in the sky. No—two little dots. Even his eyes couldn’t make it out exactly. But it looked like a man walking up there.

A man walking, high in the sky, taking great strides, pushing something ahead of him—

Then the twin dots were gone in the face of the dying sun.

Benson’s recorder whirled on, getting the sound from heaven.

In the downtown lunchroom, the man with the gold tooth paid his check preparatory to going out. At that hour, after business had closed for the day, the building was almost deserted.

Up on the tenth floor, an office manager had two girls helping him get out a belated financial report to be used first thing in the morning. On the top floor, three scrubwomen were starting their cleaning task early. In the sub-basement, the assistant engineer had taken over for the night.

All told, there were probably twenty souls in the old structure.

The man with the gold tooth waved good night to the lunchroom proprietor, went to the sidewalk—then ducked back inside in a hurry.

“Hey!” he said. “Didn’t the papers say something about a noise in the sky yesterday that nobody could explain?”

“Yeah!” said the proprietor. “Why?”

“There’s a noise in the sky now,” said the man with the gold tooth. “Sounds a little like a plane. Only there’s no plane around that I can see.”

“It’s easy to miss a plane downtown, here,” said the proprietor, not very interested. “The buildings all around stick up so far you can only see a small piece of the sky at a time.”

But he stepped to the door and looked up, as others on the street everywhere were beginning to look up. He, too, heard the weird, sourceless droning sound sifting down from the empty heavens.

The sound was abruptly swelled and then blotted out by the roar of many plane motors. Eight planes, bearing the army insignia, swept over the city. They were the planes from Fort Sheridan.

“There,” the proprietor said. “That’s what you heard: the sound of those planes in the distance— Say, what’s the matter with the building?”

The massive skyscraper on whose ground floor he had his lunchroom had seemed to tremble, then to sway.

The proprietor suddenly screamed like a trapped beast and turned to run down the street. But he didn’t have a chance.

It seemed to take many seconds. Actually only three or four were consumed.

The skyscraper suddenly collapsed a story or two in the middle, like an accordion! Sections of facing that looked small compared with the rest of the structure but were actually tons in weight crumbled off and fell. Then the building did that dreadful accordion act again, lower down—and after that the whole thing toppled, like a tall man with his feet swept out from under him.

The building was eighteen stories tall. The thunder of its fall was like the end of the world; it was heard for miles. All over town, people listened—and then started running.

But none of that would do any good for the tiny mites of humans buried in the huge collapse.

The fire engines swept up. Squad cars came. In some of the squad cars, cases of gas masks had been placed. In everyone’s mind, now, were the headlines suggesting that an enemy invasion was in the making. This building had no doubt been blasted by an aerial bomb, and perhaps gas was to follow.

But when men began to dig in the dust-clouded debris, the bomb theory was swiftly discarded, and once again mouths took on a trim line and eyes were appalled and outraged.

The steel girders—what of them were left intact enough for examination—looked like rotten cheese. They were crumbled and flawed like punk that has been stepped on. Enemy invasion? To hell with that idea! The building had fallen because, years ago, poor steel had been used in its construction, and that steel had at last given away.

The Avenger was not among the investigators.

By the time the awful rumble of the catastrophe rolled from center to rim of the city in a tidal wave of sound, Benson was at the yacht harbor basin at the controls of his personal flying fortress.

He had completed a wax recording of the noise from the sky before the appearance of the army planes drowned it out with their speeding motors, and then had raced for his plane. Now, with the Fort Sheridan ships wheeling through the air in search of something to shoot at, Benson took aloft.

CHAPTER IX

The Bears’ Den!

In the abandoned ferry, Smitty’s first task was to make sure there weren’t spying eyes around, and guns pointed at his back, before he started making the investigation ordered by Benson.

With his flash lighting a narrow path before him, he made the rounds of the hull.

A car ferry, designed to take a dozen heavily loaded freight cars on its flat, ugly top, is a tremendous thing. They’re as big as a ship and loom high from the water when empty. There is ample room in their vast interiors for an excellent hangar, though this was probably the first case on record in which one had been put to such a use.

It took Smitty a long time to search around the thing. But finally he had the rough outlines in his mind.

The interior of the hull was about eighty or ninety feet by a hundred and fifty feet. Underneath were good, sound timbers—not beach sand. The ferry might be abandoned, but it was still amazingly whole. Smitty had an idea the thing could be floated again, with only a little pumping required to take care of the leakage around the almost watertight hangar door.

It was amazingly well equipped, too. There was a small diesel motor that could generate enough power to supply light for electric bulbs studded around the hull. There were many drums of aviation gasoline and oil. There was a fairly complete machine shop in a corner.

In the other corner was a lot of stuff that puzzled Smitty very much. He was an electrical engineer of extraordinary ability; but this seemed to verge somehow into the range of practical chemistry, and it had him baffled.

In this other corner were several tanks at least forty feet long and ten feet deep. They looked like swimming pools, but with the lake right outside to be used for a pool, it was unlikely they were used as such.

Over the great tanks were light cranes, with ratio pulley blocks showing that they were operated by hand. The cranes were obviously designed to lower large objects into the tanks.

“But what,” mused Smitty, “do they dunk into these big vats, and why?”

He wet his hand from the colorless fluid in the tanks and smelled his fingers. No smell. The stuff looked like clear water. So he swallowed a sip or two—a highly dangerous thing to do with a doubtful chemical.

However, he got away with it. The stuff was water. Just plain water. The same ordinary H_20 as had been in the shallow little pans in the Gant brothers’ laboratory.

So the gang here dipped something carefully into plain water, with the aid of painstakingly erected hand-cranes! It seemed a kind of reasonless thing to do.

Beyond one of the tanks, Smitty saw several drums, about the size of the gasoline drums but set apart from them. He went to them, and saw that the tops were removable. There had been labels painted on the drums, but these had been scratched away.

A few letters on one could faintly be made out. They were: “. . . IUM . . . EARA . . .”

Smitty lifted the top of one of the drums and played his flashlight down into it. The steel cask was half filled with a whitish, fatty-looking stuff not unlike lard. Again Smitty, brilliant in electrical research but no chemist, was baffled.

He took an old envelope from his pocket, put a pinhead dab of the whitish stuff in it, and folded the paper many times around it. Benson would know what it was. The chief, Smitty had long ago decided, knew everything.

The giant wandered over to the machine-shop corner. There he found a short-wave radio transmission set operated by batteries. It wasn’t equipped to handle the special, ultrashort-wave band used by Benson, but Smitty enlarged the transmitter’s scope by a few deft, homemade additions that would have made an ordinary radio engineer’s eyes bulge with admiration.

He called the chief at temporary headquarters, and got no answer. There wasn’t any answer because MacMurdie and the chief were at that moment taking off from Yacht Harbor. And Josh Newton, at headquarters, had not yet been familiarized with the secret radio code. But Smitty didn’t know that.

He put the transmitting set back in the condition in which he had found it, and started toward the broken-plank door.

He stopped just short of it and listened hard.

Out on the lake, somewhere near, was sounding the smooth roar of a marine motor. And about two seconds were enough to tell that it was heading rapidly this way.

Smitty had prowled the bears’ den unmolested—but now the bears were coming home.

He jumped to the entrance, splashing in the breast-high water, as light-footed as a sixteen-year-old stripling, for all his giant bulk. But he saw at a glance that he was too late. He couldn’t get out of the ferry’s hull now without being seen.

Only a few hundred yards away, and skimming fast, was a large motor cruiser, with riding lights gleaming like jewels in the gathering dusk. But Smitty didn’t pay any attention to the pretty lights. He was staring at the cruiser’s deck.

He saw at least a half dozen men there, and in addition got a glimpse of a head bobbing down a hatch aft.

The giant paddled back away from the door. It was all he could do. He couldn’t get out. The best remaining course was to try to hide somewhere till he had a chance to slip away unobserved.

He chose the drums of gasoline as a convenient barricade, and slipped behind them. He barely made it when he heard the cruiser stop outside, then grind forward again at low speed and under a load.

The load, he saw, from between two close-placed drums, was the swinging weight of one of the great doors at the end of the ferry. The cruiser’s nose had been bunted against the left-hand one, and was pushing it inward. Smitty guessed that when the diesel generator was functioning it worked the big doors on motors. When it was off, the doors had to be opened like this.

The cruiser crept in till the prow grated on the ferry’s bottom timbers, which was at a point just far enough inside for the door to be closed again.

But the men on the boat didn’t close the door. They left it open, and began swarming off the cruiser.

Smitty’s brow wrinkled in disgust at the lousiness of his luck. There were even more than he’d thought. Eleven men came off the cruiser. Eleven were too many for even the giant Smitty to handle, particularly since each, of course, would be fully armed.

The last two to come off the boat carried something.

And with the first glimpse of it, Smitty’s eyes narrowed dangerously. The thing the two carried was a bundle about five feet long wrapped in sailcloth. But it was a bundle that kicked and squirmed till it was all the two men could do to handle it, in spite of the sailcloth which was used as a sort of straitjacket.

From the kicking end of the bundle two silk-sheathed legs suddenly burst free of the clogging heavy cloth. Small feet clad in high-heeled shoes were vicious twin blurs as they sought earnestly to make connection with something.

It was a girl! The gang had added kidnapping to its activities.

Smitty growled deep in his throat like an enraged bull elephant. But he stayed behind the drums. The odds were too hopeless. He could serve the girl best by waiting and trying at a later, safer time to take her away from here.

Then, with an oath, one of the two men dropped the wriggling bundle so that it splashed in knee-deep water.

“She’s a wildcat!” Smitty heard him snarl. “I think we ought to smack her with a wrench and have it over with, once and for all.”

“Not till we find out from her how much the white-headed guy knows,” the second man said. Then he cursed, too, as the dropped bundle freed itself from the clogging cloth, and a girl with her skirt ripped and her blouse in shreds seemed to soar right at his face like an enraged, leaping lynx.

Behind the gas drums Smitty hunched great shoulders in an unreasoning urge for action no matter how hopeless the odds. For the girl was Nellie Gray!

Pink-and-white, dainty, fragile looking as a Dresden doll, Nellie seemed even more softly helpless and feminine than usual with her slim body shielded only by shreds of blouse and a tattered skirt. But so does dynamite look harmless in a slim round stick.

One of the men, lunging for her, suddenly found himself splashing flat on his face in the dirty water beside her. The second felt tapering small fingers briefly clamp on his wrist, felt himself whirled a little sideways, and then fell with awkward splash over the first man.

“You dummies!” raged one of the men who had gone toward the machine shop from the boat. “Get her! Quick! Before she can start that boat!”

Like a sleek-legged wraith, Nellie was at the boat and raising herself toward the deck. But they got her! Two more men caught her slim ankles before she could draw them out of reach. The two in the water, furious at her and at themselves, reinforced them. They hauled her down with brutal force.

And then two oil drums near the port side of the ferry’s hull banged apart and an infuriated giant sprang from between them.

No matter what the odds, or how illogical it was to tackle them, Smitty couldn’t stand to see Nellie Gray knocked around like that.

Men yelled and ran for him! Others shot at him! But with only the lights of the cruiser for illumination, the interior of the vast hull was very dim; and Smitty was only a gigantic shadow charging toward the struggling group. So no bullet hit home.

The four saw him coming, and one of them swung on Nellie while two others were holding her arms. It was a man’s blow, catching her full on one satiny cheek. She slumped in their grasp—and Smitty proceeded to go completely crazy.

He got the man who had slugged her, with one great hand on a shoulder and the other on a thigh. He raised his struggling body almost at arm’s length above his head, turned and threw him bodily at the other men who were rushing to get at him.

The man catapulting through the air hit the first two men and bowled them over. But he hit them dead! Two slugs intended for Smitty tore through the thrown man’s body.

The three remaining by Nellie’s side were climbing up Smitty’s tall frame like three boys hugging a tree trunk. But suddenly the three were one! Smitty’s gigantic paws had grabbed two men by their necks and cracked their heads together. They fell like broken twigs, and one was destined never to get up again.

The rest were on the big man, now, no longer trying to shoot because of the darkness and the danger of shooting each other. A thrown wrench sailed toward Smitty’s head. He blocked it with a massive arm, stooped to pick it up.

Two men leaped to his back, pounding with clubbed guns at his skull. He heaved them off with a sudden upright lurch, and began swinging the wrench.

A man staggered back with a broken collar-bone. Another sagged with a crease in the bone of his skull over his left ear. A third screamed and pressed his hands over the place where a face had been. The others callously stepped over his body and came on.

It was a battle between pygmies and a giant. But there were too many pygmies!

A slashing gun barrel found his head, and he staggered. Another got him and he went ponderously to his knees. His feeling hands got the calf of a leg. He squeezed, and the owner of the leg shrieked with the agony of pulped muscles that would keep him off his feet for at least a month.

But that was the last. They were all over him. And then he was down—and out.

Three men had their guns at his great head. But one of the others—he of the battered felt hat who had played the part of a track foreman so smoothly in the afternoon—raised his hand.

“No! Hold the slugs,” he said thoughtfully. “What we want is information. We were going to get it out of the babe. But she may be too stubborn to talk, no matter what we do. This guy, though, might crack after he watches us work her over. Anyhow, it doubles our chances. So tie him up with everything in the place, and let him live.”

The man shook his head wonderingly.

“I don’t see yet how he and the other two got off that train in time! They sure die hard.”

The prone giant and the limp, doll-like figure of Nellie Gray were carried to the back of the ferry. Smitty was bound with cable till he looked like a mummy. And the girl, in memory of her amazingly effective struggle, was tied with more precaution than the gang would have given to most men.

The leader of the murderous crew looked toward the lake end of the big hull.

“Open the other door,” he said. “They’ll be coming back soon.”

One of the men, with a great welt on the right side of his face where Smitty’s left fist had brushed him, started the diesel generator. Lights glowed out in the ferry’s cavernous hull. And there was a hum as a small motor swung back the other hangar door.

With the entire end of the barge open, anything short of an overseas clipper could glide within. But no one on shore could see that opening. And no one on shore could see the unexpected spectacle of electric lights illuminating the abandoned hull. There were no cracks in the sound old timbers wide enough for that.

With death in his eyes, the leader of the band turned to the bound pair, to slap the girl out of her unconsciousness and make her talk.

CHAPTER X

The Flying Dutchman!

The weird noise in the sky over Chicago had completely disappeared in the thunder of the Fort Sheridan army planes when Benson and Mac got their big two-motored job off the lake. It was a full ten minutes after the fall of the skyscraper. But Benson wasn’t discouraged by these things.

In the plane was the latest thing in small sound-detectors, with amplifying tubes and a cone-shaped restrictor that could listen to one piece after another of the empty sky and meanwhile keep out all other sounds from other parts of the heavens.

Benson turned this on now and knew he had a listening device almost equal to the army’s great four-horned detectors. He began pointing it in one segment of the sky after the other, trying to pick up the weird noise again.

The army ships left him respectfully alone. A radio call to Fort Sheridan had been relayed to the service planes explaining Benson’s standing and ordering that his ship be given a working berth.

MacMurdie, bleak, blue eyes tense, stared at the pinpoint of drama in downtown Chicago where a big building had once stood.

“The cold-blooded devils!” he grated. “If I ever get a chance at them—”

“You will,” said Benson, shifting the listening ear while his plane slowly circled.

“I hope so, Muster Benson,” said the Scot gloomily. “But ’tis only a thin hope. We haven’t yet any idea of the particular devil directin’ all this.”

“Oh, yes, we have,” said Benson, pale eyes flaring their deadly light. “There are many hints.

“Our man is wealthy. It takes money to hire these underworld rats, and to fix that abandoned barge up in such a complete manner. Our man knows something about the Catawbi Railroad, or he wouldn’t be aware of the existence of the old barge in the first place. Our man knew the Gant brothers quite well, or he’d never have suspected that they were working on the inventions he murdered them to get and keep secret. Our man has some interest in publicizing the destruction of buildings, or he wouldn’t have sent an agent to tell a news reporter all about it in advance.”

He adjusted the delicate listening device again, his white, paralyzed face as expressionless as the face of death, itself.

“We shall start with the friends of the Gants. When we find one who also is rich, is familiar with the workings of the Catawbi Railroad, and has a motive for advertising the destruction of buildings, we’ll be getting warm.”

Mac’s bleak eyes narrowed pessimistically.

“But if we do find him, how will we ever prove any-thin’ on the mon? He’ll be clever as Satan himself. Too smart to leave any clues that a court of law could use.”

Benson said quietly: “Most of the men we fight are as clever as that. But they somehow pay in the end, don’t they? This man will be taken care of—when we discover him—”

Suddenly the plane banked and began racing east and a little north at five miles a minute.

“Ye’ve hearrrd somethin’?” blurred Mac. “The noise?”

“I think so. Listen!”

Benson passed the earphones to Mac, who used both of them. Benson had only pressed one to his head, listening to Mac with the other. Even so, the Scot couldn’t hear with two ears what Benson had caught with one. Not for a minute, that is. Then he got it.

“ ’Tis the dronin’ sound, dead ahead,” he said. “Ye’ve hit the direction square on the nose.”

“We’ll hit whatever makes the sound pretty soon, too,” Benson said calmly. “I’ll back this plane against anything else in the sky, normal or supernatural, for speed.”

He opened the throttle wide. The twin motors screamed as they sent the big plane forward at four hundred miles an hour.

East and a little north. Toward the weird sound in the sky. And toward a low-hanging cloud bank on the horizon that hinted at weather on the morrow less clear than the present amber dusk.

“Keep a close watch ahead, Mac,” Benson directed.

The Scotchman nodded. He heard the weird sound increasing in the earphones. Coming from an empty sky! He stared hard ahead, blinked, stared again.

“See anything?” said Benson, whose pale eyes had caught the blink.

“I don’t know,” Mac said slowly. “I thought I did. But maybe it was only spots before the eyes—”

“Or a man walking fast in the sky,” suggested Benson.

“Now, Muster Benson! How could a mon walk—” Mac broke off sharply. “There is somethin’ ahead. Two little dots, close together, goin’ about as fast as we are, right for the cloud bank.”

He pressed the earphones to his head.

“The noise has changed,” he said. “It was a drone. Now it’s a kind of whistlin’. Like somethin’ big and alive might make if it was flyin’ along in misery—Chief! Look! A ghost ship!”

Mac’s cry was unnecessary. Benson’s telescopic eyes had caught the bizarre sight before the Scot’s had.

At the fringe of the cloud bank, several miles ahead of them, the ghostly outlines of a plane were slowly appearing in empty air. But it was a plane, it seemed, that was made of fog—or was materializing from a world of dead planes and dead pilots.

Thin and gray, like the cloud-stuff itself, the thing briefly showed at the edge of the mist. A ghost plane! A Flying Dutchman of the air. Then it slid into the cloud bank, mist returning to mist, and disappeared from view.

The whistling noise disappeared from the earphones, too. The drone had faded into the eerie whistling; now that had faded into nothingness. The sky was empty of sound save for the background noise of their own motors.

“It’s gone!” exclaimed MacMurdie, freckled face screwed up. “If ye could say a thing has gone when it was never properly here in the first place. Because, d’ye see, a ghost isn’t really here to begin with—”

Benson said nothing. He was hurtling the ship toward the point where the thin and wavering outlines of the ghost plane had last been seen. He passed it in about ten seconds, and entered the clinging cloud bank.

Nothing could be seen in there. And the detector, swing it as they would, picked up no more of the odd droning or bizarre whistling.

Benson settled to three thousand feet, under the cloud bank. His pale and icy eyes had the glitter in them that came from sudden, valuable knowledge—and which meant disaster for someone in the very near future.

“We’re in familiar territory,” said Mac.

Ahead a few miles was an oblong small dot on the scalloped edge of the lake. But its tininess was obviously the result of distance. A glance told that in reality it was immense.

“The abandoned ferry,” nodded Benson. He had known precisely where they were before the sight of the barge told them. “Keep the detector turned back toward the cloud bank. Hear anything? No?”

The Scot kept shaking his head.

Benson sent the plane in a long slant toward the ferry. It was almost night, and the great scow showed only an oblong blackness on the vague white of the beach.

Even Benson could not know that the blackness had been much relieved, from the lake side at least, a moment before.

In the ferry, Smitty was sitting with his big broad back against the side of the hull. A little in front of him, placed so that he could get all too plain a view of what went on, Nellie writhed in the grasp of two men. Her slim, round arms were reddened and bruised. There was a blue patch on her cheek from the blow that had knocked her out.

She was watching the man with the battered felt hat. Smitty was watching that man, too, and straining at his bonds in a way that made the others highly uneasy, in spite of the size and strength of the rope.

The man with the battered hat was smoking a cigar, and puffing the end hard till a glowing red cone could be built up.

“You’ll answer,” he said coldly to the girl. “Or that big clown over there will answer for you. And you know what we want to hear, too. What does this guy Benson know about us, so far? And what is his next move?”

Nellie straightened to all her five feet, and she laughed in the man’s face.

“Why you little hellcat—”

The man with the cigar stepped savagely toward her.

Then a loud buzzing filled the hull of the ferry.

“The siren,” one of the men said. “They’re back—”

“Hey! This is somebody that ain’t got any business around here!” called a man from the machine shop corner of the improvised hangar. He had earphones on; he was listening to a detector a little like Benson’s only much less effective.

It had been effective enough, however.

“Strange plane!” he yelled again.

The man with the battered hat promptly forgot all about Nellie. He threw his cigar into the water, where it hissed and went out.

“Lights!” he yelled. “Everybody down. Douse the lights on the boat. Get tommy guns!”

Every light in the place winked out as the man near the diesel cut the switch. An instant later the lights on the cruiser went out, too.

“No, leave the doors open,” the man in the battered hat called as the hangar portals started to close. “Anybody coming this near must know something. We want to catch ’em, not just stay hid till they go away. With the doors open, they might be dumb enough to walk right in.”

Smitty, leaning bound against the hull, felt torment tear at him. He knew those motors. They were Benson’s. The chief was near here—coming here probably. And the place had suddenly and effectively been turned into a death trap—

The leader of this hell crew wasn’t dumb.

“Gag the big guy, and the girl,” he snapped.

Smitty got out one roaring yell as a man approached with a piece of dirty waste. But the warning was premature, he knew. It could never be heard on the plane, still far off, and insulated from sound by its own motors. Then the waste was gagging his lips; and Nellie was similarly silenced.

The giant could only sit there, sweating, with the knowledge that from every vantage point in the darkness the snouts of submachine guns pointed toward the hangar door. If the chief attempted to wade through there—

“Ye’re goin’ down to their hangar?” Mac said, in the big plane. “Why, if ye don’t mind the question?”

Benson’s dead, white face could never express an emotion. But his pale eyes looked as though they might have smiled a little.

“Even a ghost plane, Mac, has to have a hangar,” he said. “And the doors in the end of the ferry, I see, are open and inviting.”

“Then ye’re not only goin’ to land, ye’re goin’ into the ferry?”

Benson nodded.

“Ye’re goin’ to taxi the plane in?”

“Yes, Mac. And don’t ask why. The reason is obvious. The ghost ship disappeared near here. Maybe, as I said, even ghost planes can use hangars. But this one couldn’t use this hangar if another ship already plugged the room in it, now could it?”

Mac gnawed at his lip, and stared doubtfully at the innocently inviting hangar portal as Benson set the plane down on the water with a smoothness that few pilots could have equalled.

The big ship slid toward the ferry, slowed, spurted forward as the motors blipped.

In the dark hull, gun snouts poked forward with grim eagerness.

Benson slid the big plane into the hull with miraculous deftness, considering there was less than a yard of clearance at the end of each wingtip and less than a foot of clearance at the top.

The amphibian crunched gently to a stop on the slanting bottom of the ferry’s hull—

And lights burst out in every angle of the place.

At the same time the hangar doors began to close. The trap had been entered—and sprung.

But Smitty, the instant he had seen the chief piloting the plane in, instead of entering the place personally, had relaxed with a happy grin on his battered lips. And in an instant the gang in the ferry knew why.

Trapping that plane was a little like catching a tiger in a muskrat trap.

“This,” said Benson, with Mac in the pilot’s compartment, “is a little unexpected.”

“But a guid surprrrise,” burred the Scot. “Look—they got Smitty, the big numbskull. And ’tis here they came with Nellie. ’Twill be a nice party gettin’ them out of here.”

“We’ll loose a few of those special gas melons of yours, Mac—”

They couldn’t hear each other any more. The gang, inflamed with grim pleasure at the lucky fluke that had brought the enemy, plane and all, into their trap, had cut loose with every gun in the place. And for a moment they felt quite satisfied with the result.

Holes leaped into being in a dozen places in the all-metal wings and fuselage.

But only in part of the fuselage.

The pilot’s compartment was in a second metal shell, cupped within the fuselage proper, that could have turned even .50 caliber army machine-gun bullets. The submachine gun slugs were no more effective against it than so many dried peas.

They could and did drill the rest of the plane. But in there, Mac and Benson sat in serene safety.

Two glass spheres dropped from the rack under the fuselage. They hit only water; but they were so delicate that even that cushioned impact shattered them.

Within the glass melons was a gas of MacMurdie’s own clever inventing. It had such an affinity for oxygen that it rushed to fill the great cavern of the ferry in a quarter of a minute. It had such anaesthetic properties that the persons in there breathing it began to feel as if serpents coiled around their agonized throats, in another five seconds.

Not till then did the gangsters realize that their trap had been deadly only to themselves. Not till then did they see that their streaming slugs did no real damage; that slugs had passed through those wings before, and their passage been easily and quickly repaired by small duralumin disks fused over the holes.

As if in concerted answer to a raised baton, all the guns stopped at once. The gunmen were unconscious.

The pale-eyed, immobile-faced man stepped from the pilot’s compartment, with Mac close behind. A glance sufficed to show the hangar door controls. Benson threw the switch that opened them, and went to where Smitty and Nellie lay.

Unfortunately, they’d had to breathe the air of the ferry, too. But Mac’s gas wasn’t lethal; just knocked people out for a time.

Benson stooped, shouldered Smitty’s great bulk and walked back to the plane with it. Smitty weighed nearly twice as much as the gray fox who carried him. But Benson walked easily erect under the weight.

Mac came with Nellie in his arms. But the Scot rebelled as Benson closed the cabin doors, after they’d pushed the ship till she’d float slowly backward into clear water.

“Ye’re not just goin’ awa’ and leavin’ these skurlies!” he protested. “The murrrderin’ fiends!”

“What do you suggest doing with them?” said Benson quietly. It was uncanny—the complete lack of emotion in The Avenger’s voice, and the icy rigidity of his dead face in the midst of menace and destruction.

Mac pulled at his bony fingers in impotent anguish.

These men were just tools of the shrewd brain behind the gigantic destruction-plan. They could be turned over to the police—but they’d never talk, and they’d probably be out on bail very soon.

“We could kill them all,” said Benson, icy eyes reading the Scot’s every thought. “That is, we could if I hadn’t my old-fashioned ideas against executing people. But if we did—it would only delay the man behind them in his plans till he could get together another gang. And we don’t want delay.”

The cold-eyed man started the motors.

“No use staying around now. Those shots will have been heards for miles out over the lake. The ghost plane will never land now—if, indeed, it meant to before.”

Mac shrugged helplessly as the big ship took off. Odd as it seemed simply to go off and leave these murderers free, he knew in his heart it was the course of wisdom.

CHAPTER XI

Strange Revelations!

At the Gary laboratory of the Missouri Steel Corporation, Benson straightened from an analysis of two bits of steel. With him, respectfully watching the conclusion of a bit of laboratory work far beyond his own capabilities, was the head metallurgist of the plant.

The two pieces of steel had come from the ruins of the collapsed skyscraper.

In that deathly debris had been some steel girders that were whole and unflawed—among the many that were as cracked and rotten as brittle glass. Benson had analyzed a bit of the whole steel, as well as a bit of the rotten steel.

“Steel for that building,” said the metallurgist, “was supplied by us. Some of the girders were of ore from our own Pennsylvania mines. Some was of ore from the Catawbi Iron Range in Michigan. Your analysis will give a hint as to which steel failed.”

Benson was ready with the analysis now.

“In the steel that did not fail,” he said quietly, “there is a slight trace of low-grade chromium. Perhaps a thousandth of one percent. That would have placed the ore the steel came from, even without your sales records. For traces of chromium in raw ore are only to be found in a few localities, of which Michigan is one. Therefore, the steel which endured was of Catawbi origin.”

“You think that was due to the trace of chromium?” the metallurgist said eagerly. “Because it would be very easy to add the right percentage of the alloy to all our steel, and—”

“I don’t know yet,” Benson cut in. “You say you obtained access to the America Steel Corporation’s books and found out the same thing about the collapsed pavilion? That two types of steel had been used in the girders, and one fell down while the other remained all right?”

“Yes!”

“So,” Benson murmured, pale eyes flaming in his white, dead face. “Catawbi steel is not affected by these catastrophes, and ordinary steel is. Tell me a little about the Catawbi setup.”

The metallurgist explained.

“Up in Michigan there is an entire small range of hills which is almost solid iron ore. Easy to mine, near the surface, near Chicago. But the ore is so low-grade that the cost of processing it makes it a little more expensive than other ores. Therefore, most steel companies, like our own, prefer to get ore from their own mines. So the Catawbi Range is a losing proposition.”

“It won’t be if this sort of thing keeps up,” mused the gray-eyed man.

“No,” said the metallurgist, “it won’t. If Catawbi metal stands up, and all other steels collapse, the public will insist on Catawbi steel being specified in all new buildings, and the owners of the Catawbi Range can ask any price they like for their ore.”

“Who are the owners,” said Benson.

“A short-tempered old fellow by the name of Ringset, Colonel Marius Q. Ringset, owns practically all the range, with a few local Michigan people sharing the little that’s outside his holdings.”

“Ringset is a very wealthy man, then?” Benson suggested.

The metallurgist shook his head.

“It’s been a battle for years for him to sell enough of his low-grade ore to keep his range out of the hands of the banks. And the range is all he’s got.”

“Well, he’ll probably become a very wealthy man now. For he’ll have no difficulty selling Catawbi ore from now on, if I know anything about public reactions.”

As though Benson’s words could be heard miles away in Missouri Steel’s Chicago office, and also in the offices of the city engineers, at that moment the laboratory phone rang. The metallurgist answered it, listening with growing concern to an excited voice over the wire, then turned to Benson.

“You’ve hit it all right,” Mr. Benson,” he said. “That was our Midwest sales manager on the wire.”

The scientist chewed his lip.

“Missouri Steel Corporation was awarded a big bridge contract last spring. Work was about to be started on it next week. Four thousand tons of Missouri steel were to be used in the construction. Now the city has cancelled the order.”

The man stared bitterly at the bits of metal Benson had concentrated on.

“What’s more,” he said, “two big private contracts on office buildings were cancelled earlier this morning. People don’t want to put up buildings that are apt to collapse, no matter what makes them collapse—enemy invasion, poor quality, anything else. We can publish this report of yours that steel made with Catawbi ore stands up. But from now on we’ll have to use Colonel Ringset’s ore, at any price, if we want to stay in business!”

Benson went back to his temporary, top-floor headquarters.

The name of Colonel Marius Ringset had not been as unfamiliar to the gray fox of a man as he had pretended. That name had come up before. It occurred in the list of the Gant brothers’ close friends that Benson had culled from police reports for exhaustive study on his own account.

He had said to MacMurdie that the man behind the sky-walking and the tragedies of collapsed buildings, and the loss of steel track resulting in a train wreck, must necessarily fit into certain specifications.

That man would be intimate with the Gant brothers, would be well-to-do, would have an interest in publicizing the catastrophies, and would be familiar with the Catawbi Railroad setup.

So Benson had started on the list of the friends of Robert and Max Gant.

Smitty and Mac and Nellie had gone over that list with all the power of their exceptional intelligences, and had narrowed it down to three names. Those names were Arthur D. Vanderhold, Abel M. Darcey, and—Colonel Marius Ringset.

Benson, when he got back to the hotel, went over these three personalities again.

“Arthur Vanderhold,” he said slowly aloud. “Owner of the sensational newspaper which came out with the story of the building collapse, and knew of it beforehand. He knew the Gant brothers for years, and once advanced them money. He is wealthy. He lives up along the shore, uses the Catawbi Railroad, owns some of it in this commuter-shareholder arrangement, and presumably knows something about it. But as far as can be found out, he has no interest whatever in Catawbi ore. It is to his interest, however, to publish sensational news—like building collapses—before any other paper can publish them. And Vanderhold has long been known as a man who sometimes makes up his own news in order to score a beat on other papers.”

“Whoosh! Even Vanderhold wouldn’t knock a buildin’ down so he’s know of it ahead of time and have a news scoop,” Max objected.

“It doesn’t seem logical,” Benson said, dead lips barely moving in his paralyzed face. “We’ll go on to the next.

“Abel Darcey knew the brothers very well. He is rich—largest stockholder in the Michigan Builders’ Bank, which is financially interested in the Catawbi Mine holdings, and would probably profit if the mines did. He is president of the board of Catawbi Railroad, though he doesn’t own much stock in it. There seems to be little reason why he would want to publicize the building collapses.”

Benson checked the last name.

“Then there is this Colonel Ringset.

“He didn’t know the Gant brothers as well as the other two, but he saw them pretty often. His mines are not a rich proposition at present, but he could be personally well-off enough to come in our category of suspect. As owner of the source of Catawbi ore, he stands to become fabulously wealthy because of the failures of other steels.”

“Ye think one of these three is the skurly we’re after?” said MacMurdie.

“It’s probable,” Benson said. One of his characteristics was that he didn’t jump to conclusions. He had an almost intuitive sense of deduction, but he always checked up on his mental thrusts before making decisions.

The phone rang. Nellie went to it. The respectful voice that spoke to her was that of the police commissioner, himself. There was a little more information on one of the names Mr. Benson had sent in to headquarters.

Nellie came back with blue eyes sparkling.

“It’s on Arthur Vanderhold,” she said. “It had come out that he owns a large block of stock in America Steel Corporation. I guess that eliminates him. America Steel will lose a great deal of money if they have to buy Catawbi instead of ore from their own mines. And Vanderhold wouldn’t want to do anything to hurt the corporation he has so much money in, would he?”

“It would seem not,” said Benson.

He was moving as he spoke. He went to one of the three trunks that formed his portable laboratory. In that trunk was the record he had made of the bizarre noise from the sky.

He took out the record, and set it on a playing disk. From his pocket he took the two fragments of steel from which he had rasped filings at the Missouri laboratory for his test.

He set the two bits of metal on the table next to the record-playing device—the piece made from Catawbi ore on the right, the piece from Missouri ore on the left. Then he started the record going.

The giant Smitty, and bitter-eyed Mac, and fragile Nellie leaned close to hear the sound that came forth. And in spite of themselves they shivered at the recorded sound which, in three instances before, had been a prelude for death and destruction.

From the device came the monotonous, droning noise.

It tore at their eardrums, seemed to set the pictures on the walls to dancing. But it had no effect whatever on the bits of steel.

Benson played the record through four times. When he got through, the Catawbi steel was unchanged in any way. But so was the other unchanged!

Smitty sighed like a disappointed elephant.

“Blank,” he said. “And I thought—”

“The sound,” Benson said, pale eyes reflecting neither disappointment nor any other emotion, “had nothing whatever to do with the structural steel failures. So we will go ahead with our personal investigations. Mac, call on Vanderhold. Tell him what I just found out in Gary, Indiana, that the steel which holds up when other steel fails is made from Catawbi ore. See if his reaction to that statement tells you anything. Tell him anything else you please. Meanwhile, use your eyes and ears and your wits in trying to pick up some clue that might be useful.

“Nellie, go to the office of this man Abel Darcey. See what you can find out about him—both from the man himself and from his employees.”

“How about me, chief?” Smitty said quickly. The giant was no spectator. He wanted to be in the thick of things.

“You’ll come with me to visit Colonel Ringset,” the white-haired man said quietly. He stared at Nellie and Mac.

“Be very careful, you two. This gang knows all about us, now. They know each of us by sight, know where we are staying, and no doubt there are men stationed to trail and try to kill each of us. So—watch your step!”

CHAPTER XII

Murder Stroke!

In a city like Chicago there are many office buildings that, in their way, could be called “tenements” just as many apartment dwelling places are tenements. There are office building in neglected neighborhoods, old and shabby and dingy, waiting to be torn down and meanwhile, rented for whatever they will bring.

It was in such a building, on the west fringe of the Loop, that Colonel Ringset had his office.

Ringset was his own ore salesman. He had this little office to which he came from Catawbi every day, and out of which he sold the few but large orders that kept his mines barely solvent. There was a spinster secretary and office girl, and that was all there was to the office end of Catawbi Mines, Inc.

Colonel Ringset was a tall old man of seventy, with biting gray eyes under bushy white brows. He barked instead of talking. He had a temper that was notorious. He had an arrogant hawk nose and a ruthless, bony jaw.

He had bought the Catawbi Range as worthless land, forty-eight years ago, and had later developed the iron mines. But even his driving power and ingenuity had been unable to squeeze from ore, which was higher-priced than any one else’s, the millions to which he was entitled.

Meanwhile, he did what he could. He shipped his ore to Gary, Indiana, and South Chicago on the Catawbi Railroad, under a special rate. He borrowed from one bank to pay overdue interest on mortgages held by another; got new loans just when it seemed he must lose all his holdings; managed to keep his chin above water when almost any other man would have drowned.

Most people didn’t like Colonel Marius Ringset. But they didn’t say so. For he was a savage old fighter, dangerous in spite of his seventy years.

His spinster secretary was out to lunch when Smitty and Benson entered the ancient office-building doorway at one o’clock in the afternoon.

“Ratty old place,” Smitty observed, as they got into an ancient elevator.

The operator, a bleary-eyed man as old as his cage, sent the contraption upward. It creaked and jerked and groaned ominously. The colonel’s office was on the top, the ninth floor.

At the door with the marking, CATAWBI MINES INC., on it, Benson stopped the giant with a gesture.

“Stay in the outer office, Smitty. Look around while I’m inside with Ringset.”

“Look around for what?”

Benson’s eyes were lambent, cold flame.

“Look for orders, for any kind of material whatever, sent to the Warwick Corporation in New Jersey.”

Benson opened the door, then, and walked into a large but dingy outer office with a deserted desk and chair in it. He went on through to the door marked PRIVATE.

Smitty stood so that he wouldn’t be seen when that door opened.

Benson tapped on it.

“Come in, come in,” snapped an irascible voice.

The gray fox of a man opened the door, went in, and shut the door behind him again.

“Who are you?” said the hawk-nosed old man at the desk. He went on without giving a chance for an answer. “If you want to buy Catawbi ore, you’ll have to compete with the others in the regular way. People have found out what good steel the ore makes, now. A lot of ’em want to buy. And the supply is limited. Send me a letter stating the price you’ll pay and I’ll compare it with the rest—”

“I don’t want to buy steel,” Benson said quietly. “I came for a few words with you about the skyscraper that collapsed yesterday. And the Lincoln Park pavilion that went down. And the missing two miles of track and the wrecked depot on the Catawbi Railroad.”

Colonel Ringset stared at the man with the snow-white hair and dead, white face with his savage old eyes unreadable. He was a man who would play a marvelous game of poker.

“Why come to me about these things?” he barked. “I don’t know anything about them.”

“I came,” said Benson, “because the accidents are so complimentary to Catawbi steel.”

The cold glare from Benson’s colorless eyes and the deadly expressionlessness of his white face were beginning to eat at the colonel’s will like acid on metal. But he tried to bluster it off.

“What the devil do you mean?”

“In the case of the building collapse, some sound girders were found—of Catawbi steel. The same thing was true of the pavilion collapse. In the case of the missing rails, toward the end of the section where they’d vanished, a few rails were lying untouched. They were, I discovered later, of Catawbi steel.”

“Well?”

“It has not yet been determined what has caused the steel made from competing ore to fail,” said Benson. “But whatever it is, it leaves Catawbi steel untouched. That means that the market for Catawbi ore will suddenly skyrocket. You’ll be able to see all you can mine, at your own figure.”

The colonel’s veined old face began to get purple.

“These catastrophes will leave you a very rich man,” Benson said quietly. “That’s why I came to see you about them.”

“Why, you young—” the colonel choked. “You’re insinuating that I had something to do with those things that have taken several dozen lives—just to increase the market for Catawbi ore? Get out of here before I throw you out, old as I am.”

It was a fine exhibition of honest rage. Benson faced it with his dead face as immobile as wax, and with his cold, pale eyes unmoved.

Meanwhile, those inexorable eyes were ranging the old office.

There was an iron rack in a corner. A water-cooler stood next to a screen which surrounded a washbasin. Several chairs were placed around the walls. Near the window was the great mahogany desk at which Ringset was seated in a heavy, old-fashioned swivel chair.

Benson’s purpose was to see if there was any filing cabinet or other hiding place of business papers in here. There was none. All were in the outer office where Smitty soundlessly searched. No telling, of course, what was in the furious old man’s desk; but that was the only place in the room where documents could be concealed.

The colonel’s eyes had grown almost as cold as Benson’s own, though in their depths could be seen a lurking, growing fear of the man with the dead face.

“I won’t ask you by what authority you come here and say such things,” he barked. “I assume you have such authority or you wouldn’t dare such a thing. But I do say this: no matter if you’re from the mayor’s office, or from the police commissioner—or whoever is backing you—you’ll find, if you don’t get out of here, that I can swing enough influence to break you.”

Benson paid no attention at all to the angry words. His deadly pale eyes bored into Ringset’s.

“Skywalker,” he said.

The colonel blinked.

“What?” he mumbled, looking bewildered.

“The man who walks the sky,” said Benson. “The sound from the sky. These things are the secret of the tragedies—which will make you rich.”

“I don’t know what you’re talking about! Skywalker! No man can walk in thin air. Or isn’t that what you mean?”

The perplexity on the colonel’s face seemed genuine. Then it faded into wrath again.

“But no matter. It isn’t important what’s in your mind, behind your raving. I’ve told you to get out! And if you don’t—”

He reached for his desk phone.

Benson had done what he came to do. All he’d wanted was to anger the colonel to the point where slight noise of a search in the next room would not be apt to be heard. He had succeeded in that. And Smitty must be through by now.

“All right, I’ll go,” said Benson, continuing to play the part of a blundering regular investigator behind whose bluster was no real information. “But I’ll be back—if there are any more failures of competing steel with more lives lost.”

He went out, leaving Ringset utterly speechless with justified outrage.

Smitty was in the hall. They went to the rickety old elevator together. Benson glanced at the giant, question in his eyes.

“No record of any contact whatever with the Warwick Corporation,” Smitty said. “Nothing else that seemed the least bit incriminating, either.”

The elevator door clanged open. They stepped into the cage.

“Down,” Benson said, tone absent, pale and deadly eyes absorbed.

The cage groaned and shivered, started down—

The aged elevator operator screamed suddenly, high and shrill like a trapped animal.

Now and then a man is molded whose coordination of eye and body, brain and sensory perception and muscles, is so perfect and instantaneous that he seems able to make the movements of all other men seem like slow motion. Dick Benson was such a man.

His mind was intensely occupied with things having no connection whatever with an old elevator cage. Just the same, in a fraction of a second his brain caught the deathly significance of a sudden lurch that was more abrupt and extreme than any previous jerk of the elevator had been. He divined the meaning of it even before the old operator, who had been running elevators so long that he could fairly feel something the matter almost before it could happen.

But whereas the operator simply screamed in horror when he felt the parting of the cable that held up the cage, Benson moved.

The man had started the cage downward before he had quite closed the ninth-floor doors, as most operators do. The doors were open six inches or so when the elevator gave that sickening lurch in its worn slides. Benson got his hands in that opening, with steely fingers clamping down on the metal sill of the sliding doors.

The cage fell eight inches, and stopped. It stopped because the top of it banged on Benson’s head and shoulders, and those shoulders and head were held by Benson’s vicelike grip on the ninth floor sill.

The cable had parted above the cage. Only one thing kept it from falling ninety or a hundred feet to the bottom of the shaft. That one thing was Benson’s tormented grasp. Benson hung by little more than his fingertips. The elevator, with two other men in it, hung on Benson.

“Smitty—” the white-haired man gasped, his paralyzed features remaining expressionless.

The giant, face white with realization of how Benson must have been dazed by the sag of the elevator on head and shoulders, reached to open the elevator doors a little more and get his own great hands through.

“Move . . . very . . . gently—” said Benson, in a ghost of a whisper.

The giant was across the elevator as smoothly as a ballet dancer. The operator stayed at the useless controls, not daring to breathe.

Smitty got the sliding doors open another foot, and took on Benson’s inhuman burden, just in time. The white, strained fingers slipped, with the long drop to the bottom of the shaft seeming to reach up and drag the car.

Now Smitty hung like Atlas, with the cage-top pressing down on his vast bowed shoulders, and with only the grip of his two hands thwarting the deadly fall.

Benson took several great breaths, then was at the giant’s side. Together they heaved up a little.

No other two men in the city—perhaps in the entire country—could have done it: could have raised the unsupported cage with only the straining muscles of their arms alone. But these two did.

They got the cage up so that instead of a three-inch crack between its top and the ninth-floor sill, there was an eighteen-inch opening.

“Can you hold it here, just a little while?” said Benson.

“I . . . think . . . so,” panted the giant. His hands were as white as chalk with the strain, and his arms were trembling like great bass-violin strings.

Benson writhed out of the opening onto the floor of the corridor.

Had Smitty’s hold weakened then, his chief would have been sliced in two between car-top and sill. But the giant hung on.

Benson raced to the roof, to the elevator-cable control room. The end of the supporting cable had snapped back up ten feet when it broke. Benson’s deadly eyes flamed like ice under an arctic moon as he saw the broken end.

It had been cut by a hacksaw through nearly three-fourths of its thickness, so that the slightest extra strain—like that of starting the old car down from the ninth floor—would snap the steel strands.

“Smitty—get ready to take just a little more,” Benson called down.

And he dropped lightly on the roof of the cage.

He had won clear, and was safe. Now, by lowering himself to the car’s top he was putting his head into the jaws of death again. But a leader does that kind of thing for the safety of his men, if he deserves the title, chief.

Anyone who has ever tried to tie a knot in steel cable knows what a long-drawn-out, almost impossible task it is. But Benson’s incredibly strong fingers got the broken end of the elevator cable under the top supporting girder, and twisted the woven steel strand into a single pretzel-shaped bow, in about the time it would take an ordinary person to do the same thing with wrapping twine.

“All right, Smitty!”

Benson heard the giant groan; then the cage was dropping as the great hands were withdrawn and the cage was unsupported.

It dropped a foot, jerked to a stop as the loose bow in the tied cable tightened. Steel shrieked on steel as the bow continued to knot in on itself and as the elevator continued the slow sinking downward. Then its passage was stopped. The knot held.

Benson helped the shaky giant out of the cage on the eighth floor. He hauled the operator out bodily; the man had fainted minutes before.

Smitty managed a trembling grin.

“We tell Mac and Nellie to watch out because somebody might trail ’em and try to kill ’em,” he said, “and we get it in the neck ourselves. I wonder how—”

He said no more.

Steel cable is slippery stuff. The large bow Benson had bent in it had been quivering into a smaller and smaller knot under the elevator’s weight with each passing second. Now the sawed end of the cable had slipped at last through the loop of the knot, and let the cage go!

With a squeal against ancient slides, it rocketed downward. And then, far below, it hit! There was a smash that rocked the building, and the wood and steel of the cage became a sort of dreadful porridge of crushed wreckage.

In the center of that porridge there would have been three pulped bodies had it not been for Benson’s superhuman swiftness, and Smitty’s gigantic strength.

CHAPTER XIII

No Sale—No Suspect

You could fairly feel the tensity in the city that afternoon.

The rain clouds had cleared and the sky was bright with sun. The entire city of Chicago seemed to cower under the clearness like a gigantic, frightened beast, and to peer upward in apprehension.

From the sky, on two successive clear days before, had come a droning noise with no visible thing making it. And following that had come disaster. Would a third tragedy come from the clear sky today?

Something moving in the sky. A man “walking” there, according to a few wild accounts. Something trailing over the city and leaving catastrophe in its unseen wake.

Would that happen today?

Up in his temporary headquarters, Benson was integrating the reports of Nellie Gray and Mac, and digesting the knowledge they afforded.

“Vanderhold seems as innocent of any of this as a babe,” the dour Scot had reported. “He was at home, not at his newspaper, when I got him. He was in a flowered dressing gown, eatin’ a breakfast big enough for a gorilla, and lookin’ over his own paper. A big, fat, bald-headed guy with pockets around his eyes. I told him about Catawbi steel bein’ the one that held up. He didn’t seem interested. I asked more about how that reporter of his got advance news of the building collapse. He told me about not knowin’ anything about it for a solid half hour.”

“You saw nothing out of the way?” Benson had asked.

“Well, one thing that might have meanin’,” the Scot said doubtfully. “There was a letter near his orange-juice glass; one of a lot that’d come in the mornin’ mail. It was open; so I got a glimpse of it. Somethin’ about the Catawbi Railroad. I couldn’t see who it was from or anythin’, but I got just a couple words before he tumbled that I might be looking at it and folded it shut. I think the letter was something about buying the road.”

“Somebody wanting to buy the Catawbi Railroad?”

“That’s what it looked like. Vanderhold has a share, as a commuter on it, of course. But I don’t see that it means anythin’, Muster Benson.”

Nellie Gray’s report had seemed equally fruitless.

“Abel Darcey is all up in the air about the things that have happened to the railway. I posed as a girl reporter and got him talking about the wreck and the depot collapse. He has no idea what could have caused the two miles of track to disappear, but rather thinks the rails were stolen for their value as scrap—though he admits it would be pretty impossible to have done it. When it comes to the depot falling down, he just gives up. He says he hasn’t the faintest notion why that happened.”

Nellie referred to some shorthand notes she had made.

“He O.K.’d an order for more rails while I was there. And the specification was that they be made of steel from local Catawbi ore.”

Benson merely nodded. His finding at the Missouri Steel Corporation’s laboratory that it had been Catawbi steel which bore up in the collapses, was definitely known around the city, now. Almost any order for steel would have the same specification: made from Catawbi ore.

“Anything else, Nellie?”

The fragile-looking Dresden doll of a girl had hesitated a full minute. She knew Benson’s passion for precision of details and didn’t want to report anything meaningless.

“I think,” she said finally, “that Mr. Abel Darcey’s life may be in danger, though I don’t believe he knows it.”

“What gave you that impression?”

“You said that out at the Gant brothers’ house you found a pair of shoes in the laboratory with no nails in them—looking as if someone had stolen the nails.”

“Yes!”

“Well, as I was going out of Mr. Darcey’s office, I saw a boy leaving the outer office after delivering a bundle. The bundle looked like a pair of shoes. I caught up with the boy and asked him about them. He said they were Mr. Darcey’s shoes. His secretary had sent them to the shoe repair shop nearby, to have them nail the rubber heels back on. The soles were sewn, so they were all right. But the cobbler had received the shoes with not one nail in the heels. As if somebody had pulled them out.”

Benson’s almost colorless eyes were on her like brilliant agate.

“It looks,” she said, “as if whoever had entered the Gant laboratory and searched—and took those shoe-nails—had also been in Mr. Darcey’s office to search for something, and had done the same thing to a pair of his shoes.”

“And later,” Mac had put in softly, “the skurlies murrdered the Gant brothers.”

“Yes,” said Nellie. “So maybe the same thing hangs over Abel Darcey.”

A little information concerning the three men Benson had picked as possible leaders of that mob in the hangar. Very little! But the gray fox of a man had mulled it over in his mind, behind unreadable, colorless eyes. And now came the next orders.

“Josh!” The white-haired chief addressed his colored associate.

The sleepy-looking negro, Joshua Newton, stepped forward. Sleepy-looking? Yes, but with an intelligence in his eyes that belied his indolent look and the illiterate dialect he used with strangers.

“I want you to go to Ringset’s office. He knows you, from his visits to the Gant house, doesn’t he?”

“Yes, sir,” said Josh.

“Very well. I want you to tell him in a roundabout way that you have an idea what the inventions of the murdered brothers were. Tell him you’ll sell your knowledge of those inventions if the price is right. See how he reacts to that.”

“Yes, sir.”

“And Josh,” said Benson. “Walk up. Don’t use the elevators.”

“There’s nothing like climbing stairs to preserve health,” Josh agreed.

“Oh, now, Sleepy,” Smitty said. “You know you wouldn’t climb nine flights of stairs unless your life, itself, depended on it. Why you never move at all if you don’t absolutely have to.”

“Neither does a cat,” pointed out Josh, who was something of a dusky philosopher. “But a cat’s usually in good health, isn’t he?”

The Negro shuffled out, deceptively sleepy and dull-looking.

Benson’s bleak, agate eyes turned on Smitty and Mac.

“I want you two to cruise along the Catawbi Railroad right-of-way again, and look around the spot where that track disappeared. Also, question more of the farmers around there, and see if any others besides the one I talked to happened to glimpse anything in the sky when the noise was heard.”

There were left the two girls—pink-and-white Nellie Gray, and darkly pretty Rosabel.

“Nellie,” Benson said, “you will go to Ludlow, the lake-resort town farthest north on the Catawbi line. After our discovery of the abandoned car ferry they’re using for a hangar, the gang will have towed it to a new spot. There’s only one direction to tow it to a deserted spot and that’s north, away from the city. Probably near Ludlow.”

“And I’m to look around for it?” Nellie began eagerly.

“You are not,” said Benson. “You will go to Ludlow as a wealthy young heiress with nothing on her mind but boating and swimming. There, you will simply keep your eyes and ears open and see if you can find out anything from the local residents. This gang will probably have a few of the local tough boys in their employ. You may learn something. Rosabel, you go with Nellie as her maid. It will make the heiress act look more natural, and you can help if anything happens. Can you shoot?”

“Yes, sir,” said the colored girl quietly. She turned away for a moment, lifted her dress, and turned back with a gun in her hand—the smallest make of .22 palm-gun. It was hardly larger than a watch-charm; but at close range in an accurate hand it could do deadly things.

Benson nodded, colorless eyes inexorable and steady in his paralyzed, white face.

“Don’t take unnecessary risks. Simply learn what you can by talking around. Mac and Smitty will meet you later at Ludlow’s best hotel. You’ll all get further orders there.”

Joshua Elijah Newton shuffled toward the old office building in which Colonel Ringset had his office, on tired-seeming, enormous feet. He was going to approach Ringset in his habitual role of uneducated darky. Only a few knew him as he really was—highly educated, alert, clever.

Colonel Ringset, who had not come to the Gant home as often as a few other friends of the brothers, was not one of those few.

“The hunter,” Josh often told Rosabel, “doesn’t turn his gun on the turtle as quickly as on the weasel. Folks don’t watch the slow and dumb like they do the swift and smart. Always be a turtle till you see if the man you’re talking to is a hunter.”

Colonel Marius Ringset, Josh had decided the first time he laid eyes on him, was a hunter. Whether his hunting was of the kind approved by society or not, Josh hadn’t known or cared—till now. Now Mr. Benson wanted to know; and what that gray fox of a man with the icily flaming eyes wanted to know, Josh was going to find out for him if it was humanly possible.

Josh entered the dingy lobby of the building on slow, huge feet.

There was an out-of-order sign on the furthest of the two elevator doors. He heard a clanging in the basement where a man was still clearing away the debris of the smashed cage Smitty had told about. But there were no police around.

It looked as if the accident hadn’t been reported to headquarters, although the saw-marks on the steel cable must have told that the “accident” was an attempt at murder.

The suspicious failure to report such an accident might be caused by Colonel Ringset’s orders. Or it might be that the building owner had simply wanted to avoid notoriety for his building, which would exonerate Ringset of crooked motives.

Josh shuffled up nine flights of stairs and walked into the outer office of the colonel. A waspish woman of forty stared at him from behind her desk.

“Ah’d lak t’see de cuhnel, please, ma’am,” Josh said, hat in hand.

“Colonel Ringset is very busy just now,” the waspish secretary said, “I’m afraid—”

“Ah’s de boy worked fo’ Robert and Max Gant,” Josh said. “De cuhnel knows me. Jus’ tell him Ah’s anxious to see him, please, ma’am.”

The spinster secretary frowned, hesitated, then went into the office marked Private. She came back in a moment still frowning, but less impatient of manner.

“He’ll see you.”

Josh shuffled into Ringset’s office. The cold, gray eyes of the old man probed him from under bushy gray brows.

“Your name’s Josh, isn’t it? Yes, I thought I remembered— Terrible thing, the brothers’ deaths— What did you want to see me about, Josh? A job?”

“No, suh,” drawled Josh. “Leastwise, not ’zactly. But it was about money.”

“If you want to borrow”—Ringset began, scowling.

“No, suh. Ah don’t want to borrow. Ah’s got somethin’ to sell and Ah thought mebbe you’d be interested.”

“Something to sell? I don’t understand.”

“It’s lak this,” drawled Josh, turning his hat in bashful fingers. “De Gant brothers was wuhkin’ on a couple inventions when dey was killed. Seems lak dey was pow’ful inventions, too. Now, folks thinks dem inventions is gone an’ fohgotten, with the brothers daid.”

“Well, aren’t they?” said Colonel Ringset.

“No, suh,” said Josh earnestly. “Leastwise, Ah don’t think they is. Ah knows where Ah can put my han’s on some papuhs of the brothers. Dem papuhs has somethin’ to do with the inventions. Ah’s daid sure o’ that.”

The cold, old eyes were very steady on Josh’s face.

“So?” Ringset said.

“So fo’ a little money—say a hun’ded dolluhs—dem papuhs could be turned ovah to you-all, cuhnel. And from de papuhs, mebbe you-all could figure out what dese pow’ful, big inventions was. An’ dat would be wuhth more’n a hund’ed dolluhs, wouldn’t it?”

The colonel’s gaze was still intent on Josh’s sleepy, innocent-looking face. And in the old man’s eyes Josh could read—nothing at all. Mention of the Gant inventions hadn’t caused the old man to turn a hair. Mention of papers which someone else might buy if he didn’t, seemed to mean nothing to Ringset.

“Josh, you’re a black rascal,” the colonel said after a moment, lips thin.

“If a hund’ed dolluhs is too much,” faltered Josh, “mebbe fifty dolluhs—I”

“You can leave, Josh. I don’t want any inventions that way.”

“But f’um de way de brothers talked dem inventions might be wuhth millions—”

“Not interested,” said Colonel Ringset coldly. “You can go, now. I’m very busy.”

Josh left, a picture of disappointed docility.

He really was as disappointed as he looked. He had hoped to learn something for Mr. Benson. But there had been nothing to learn from the colonel’s reception of an offer that you’d think any man, if he were the least bit crooked, would jump at.

So it began to look as if the mine owner, no matter how he stood to profit from the steel failures, was as honest as his actions made him seem.

Mechanically, Josh started to press the button beside the one remaining elevator shaft that was in working order. Then he grimaced, went to the stairs, and descended on foot.

“A man who takes useless chances is a man who likes flowers—in hands folded across his chest,” was one of the axioms in his book of philosophy.

And yet, in spite of his precaution about the elevator, Josh took a chance when he stepped from the office building door without looking carefully around first.

Next to the building was a small warehouse, not in use, with a dust-smeared show-window and a setback doorway.

In the inclosure of that setback a man was standing. He was about twelve feet from the office building doorway.

His pose, leaning against the jamb with his hands in his coat pockets, was such that the few people on the sidewalk not far away paid no attention to him.

Josh started to walk in the other direction from the office-building exit.

“Come here, you!” came a low voice from behind him.

He turned, saw the man in the doorway, and froze.

The muzzle of a gun was plainly to be seen poking out the fabric of the man’s coat pocket.

Josh’s big feet itched for flight. And he trembled on the verge of it. But the distance between him and that gun was too short. The gunman couldn’t miss.

“I said—come here!”

Josh obeyed orders. He drew near the setback doorway of the unused warehouse on reluctant feet.

The man with the gun concealed in his pocket backed through the doorway.

“Come on! In here—unless you want a slug in the heart!”

Josh followed the man inside. It was as dark as a cave in there.

“Turn around!”

Josh turned.

The ceiling seemed to bang down on his skull, and he fell into blackness.

CHAPTER XIV

Murder Rides The Rails!

Looking demure and lovely and helpless, Nellie Gray sat on the train going north along the lake to Ludlow, a town about ninety miles from Chicago on the east shore. Nellie did not have to pretend to be a wealthy girl. She was extremely wealthy. With all the gold of the Aztecs hidden in Mexico in a cache known only to Benson and his aides, Nellie, as well as each of the others, was fantastically rich. But no one of the little group had any desire to just sit back and have a good time on that wealth. Each wanted to fight crime; since each had suffered greatly from criminals.

Sitting beside Nellie, the perfect picture of a lady’s maid, was Rosabel. Actually, the two girls were co-workers and friends. But you wouldn’t guess it to look at them. The picture was of a spoiled rich girl and a patient servant.

“What time is it, Rosabel?” Nellie said, making her voice petulant.

“Quarter of four, Miss Gray,” Rosabel said.

“And this smelly old train won’t get to Ludlow till half-past four?”

“Tha’s right, Miss Gray.”

“I’ve never been on such a train!” Nellie fumed, for the benefit of listeners. “It stops at every farmer’s back door. I’m quite sure they deliver newspapers and laundry from the engine.”

Her words weren’t much exaggerated. There was no such thing as express service on the Catawbi line. It existed only to serve the dwellers in towns along its tracks; so it stopped at each and every one of those towns.

In the middle of the afternoon, there were few on the train. Some tired-looking women, commuters’ wives who had gone into the city to shop. A few men coming home from the office early.

At each stop, some of these got off. The train kept getting emptier and emptier.

Nellie and Rosabel both heard the beginning of the talk. It was between two men in the seat behind them, and the conductor.

“Bill,” one of the men said to the conductor, “what happened to that old car ferry that was stranded on the beach a couple miles back from here?”

The two girls held their breaths to listen, meanwhile staring out the window as if not hearing at all.

“I don’t know,” the conductor replied. “I noticed this morning it wasn’t there. That’s all I can say.”

“Must have floated away during the night,” said the second man.

“But why?” objected the first. “There wasn’t any storm. A little wind, maybe, but not enough to float the ferry free. It’s been there for years.”

“You can’t tell how much wind it would take, from the length of time it’s been there,” the conductor argued. “Maybe the sand’s been washed away from under it all these years till finally, last night, it just naturally floated off again. But it don’t make much difference. A thing as big at that is bound to be located about as soon as it’s beached again.”

The conductor went on down the aisle. And Nellie and Rosabel turned their gaze from the window—to see a man just sitting down in the seat opposite them. They’d been so interested in the talk about the ferry that they hadn’t noticed him walking up the aisle from another car.

The man had his head down a little so that they could not see his face because of the down-turned brim of his hat. There was a newspaper in his hands. He spread that out, as if to read, but instead raised his head and stared squarely at the girls.

With a sort of electric shock running through her, Nellie saw that it was the smooth, blond-haired young fellow she had met once before under the name of Carlisle.

Her hand—and Rosabel’s, too—was reaching stealthily for a gun. Hers in her purse, Rosabel’s somewhere under her discreet black servant’s dress.

“Don’t,” advised Carlisle, sunny eyes crinkling as if to a good joke.

Both girls saw his right hand, under the extended newspaper. There was a revolver in that hand! The revolver had a silencer on it. No one else could see the silenced gun because of the clever way Carlisle held the paper. But the girls could see it, all right!

Nellie stared out the window. At this point, a road went parallel with the track for a few miles. On the road, pacing the train, was a gray-blue sedan.

Carlisle could kill them both with the silenced gun, get off the train, and escape in that car which was keeping pace with the train before other passengers, unwarned by the sound of the muffled shots which would be drowned by the noise of the train, could figure out what had happened.

That Carlisle would kill them if they tried to cry out, neither girl doubted for a moment. The smiling murder in his sunny blue eyes was too apparent.

“What do you want of us?” Nellie said, tone pitched low so that the men in the seat behind wouldn’t be warned of trouble and try, with well-intentioned clumsiness, to interfere.

“I just want to ride a little way with a charming girl,” Carlisle smirked.

“How far is a little way?” said Nellie.

“To the last stop this side of Ludlow,” Carlisle said.

The road beside the tracks swerved off inland. The sedan, which had been keeping pace with the train, went out of sight. But that didn’t cheer Nellie up any. The road, she knew, was nowhere farther than a mile from the track, from here into Ludlow. So at any point Carlisle could flip off the train after murder, and be sure of a quick getaway.

“Why do you want to ride there with us?” Nellie said.

The gun under the spread newspaper was very steady. So was Carlisle’s voice. Steady, and yet almost amused.

“Because,” he said, “we’re going in for a kind of roundup. The last roundup, you could call it. You and the dead-pan guy you’re working for, and the big ox called Smitty, and the others, have gotten in our way too much. So the lot of you are going to be collected in one spot, and then finished off.”

“If we’re going to die anyway,” Nellie said, “we might as well have something to show for it. I don’t believe you could get us both before one of us got you—”

The hidden gun jabbed forward a little under the newspaper. For an instant there was more murder and less smile in Carlisle’s sunny blue eyes.

“You know very well I could get you both before you could make an effective move,” he said quietly. “I will, too, if you try anything. So you can die now, or live a few hours longer by sitting still like good little girls. Take your choice.”

Nellie and Rosabel relaxed, with the hidden gun covering them.

Smitty and Mac, by the time four o’clock approached, had gone once more over the stretch of the Catawbi right-of-way where two miles of rails had disappeared. They had questioned farmers, as Benson ordered. They had picked up no additional information that—as far as they could see—had any value.

Two other farmers had heard the noise in the sky before the track vanished. They had seen nothing up there. The one with the extra-good eyes was the only one who had seen the man “walking” up there.

There was still no trace of the vanished rails anywhere around the countryside.

“We’re licked,” Mac said gloomily. “The man behind this is too clever for us. Not one trace has been left as to how he has done these things. Indeed, we don’t even know yet just what he has done.”

“You should have been an undertaker,” said Smitty.

“And why do ye say that, ye overgrown clown?”

“Because it’s the only place I can think of where such pessimism would be a business asset,” Smitty grinned. “Licked, are we? I’m betting that the chief has this whole business in a neat pigeonhole, with nothing left to do but collar the man who thought it up.”

The two had rented a car in Gary, Indiana. They were rolling up the road beside the Catawbi tracks, now near it, now a mile or so away. They’d get to Ludlow soon, and meet the girls there.

“I wonder where the skurlies took the car ferry?” Mac mused. He was driving.

“Up north farther, as the chief guessed. They couldn’t tow it any closer to Chicago, because the beach gets so crowded that it would instantly be seen.”

“Twill be spotted soon enough wherever they take it. A thing as big as that.”

“Probably,” said Smitty, “the gang only wants to keep it away from public notice for another few days, while they finish up this thing—whatever it is—that they’ve begun. There are wooded patches along the beach where they’d have a good chance of camouflaging the ferry so it couldn’t be seen well from the air, and they could expect to be undisturbed for at least a little longer— What’s that?”

“What’s what?” said the Scot, inching the speed of the car down a little.

“The motor had a funny sound in it,” said Smitty, inclining his huge head toward the dash.

“I didn’t hear a funny sound. Ye’re hearin’ things.”

“It was a kind of a drone,” said Smitty.

The road was near the track, at this point. Far ahead, they saw the train due into Ludlow at four-thirty. What with its numerous stops, they were going faster in their rented car than the train was. They’d caught up with it. They saw it slowing in the distance for a small depot.

The depot was of the kind that had collapsed along here awhile before; used by so few passengers that there was no regular attendant in it, save during rush hours. The rest of the day it served only as a shelter from the weather for the few who boarded trains from this section.

The road swung from the tracks again, and Smitty and Mac lost sight of the train just before it stopped at the depot.

“There! You can hear the drone again,” said Smitty. “In the motor— No, it’s not in the motor!” He turned to the Scot. “Mac, slip the clutch, cut off the motor, coast! I want to listen!”

MacMurdie coasted in neutral, with the car motor shut off. And now, with only the whine of their tires to distract them, they both heard the other noise plainly.

A monotonous drone. From the sky!

“The skywalker!” Smitty said, great hands clenching into fists.

Mac, without a word, jammed his foot on the starter, got the motor going again, and crammed into high gear. Then he started down the road as fast as the rented car could take them.

“Hey! What’s the idea?” yelled the giant over the rush of wind.

“That train!” said Mac, through shut teeth.

“What about it?”

“Last time that noise sounded out here, there was a train wreck. Now the noise is soundin’ again—but they can’t hear it on the train because of their own noise. I want to catch up to the train and flag it to a stop—before it gets wrecked, too!”

But they were not to do that. There wasn’t the time.

They swung back on a long curve with the meandering road, and could see the train again. But it was a mile ahead, with no more stops now till Ludlow was reached. They’d have to drive the car at eighty or better to catch up with it.

Mac had the accelerator to the floor. He and Smitty could hear the weird noise from the sky even over the racing motor, now that their ears were tuned to it. Smitty was looking out the window and up. But there was nothing in the sky to be seen.

“If the skurlies take the rails again—”

But it was not a stretch of railless ties that was to doom this train.

From the speeding cars on the track beyond them, Mac and Smitty heard a sudden rhythmic, heavy pounding, like a giant’s hammer.

“Flat wheel,” said Mac, wetting his lips.

But both knew it was more than that. An ordinary flat wheel doesn’t develop as swiftly and exaggeratedly as that.

The train was about a half mile ahead of them, now. The track was a hundred yards from the road, there. They could see it fairly plainly.

And they wished, afterward, that they hadn’t been able to.

They heard the hammering swelled to a sudden chorus of similar pounding. Then the five-car train seemed suddenly to go all the pieces, like a jigsaw puzzle spilled on the floor.

The engine sank like a runner whose knees have buckled under him. Its nose plowed into ties and sand, caught; then the locomotive tried to turn a somersault. It was thrown down. Behind it, the car bodies were dragging along the rails with no wheels under them. They kept the engine from somersaulting, but the front car was lifted high with the leverage.

As in all such movements of extreme stress, action seemed to be slow—though you knew it was proceeding, really, with appalling speed.

Slowly, it seemed, the five cars of the train looped to right and left off the tracks, and hurled themselves like five mad beasts on the wounded locomotive. Slowly the cars and engine piled over each other like jackstraws. Slowly the whole dreadful mess came to a halt in a cloud of dust and splinters.

There was silence, in which the last remnants of the droning noise in the empty sky sounded out. Then that, too, was gone, and a chorus of screams and of hissing steam rose from the wreckage ahead.

Mac and Smitty skidded to a stop on the road beside the wreck, and ran across sandy waste from road to track.

“The murrrderin’ skurlies!” Mac ground out, as he saw a man crawl from the wreckage, stare blankly around, and then collapse. The bitter-eyed Scot shook his fist at the empty sky, from which had come the noise. “They’re fiends, no less, to do these things!”

He began hauling debris aside in a feverish search for passengers who might still be alive. Beside him Smitty, with the strength of a bull elephant, did the same.

But both, in the midst of the work, could see at a glance, all too clearly, what had caused the wreck.

The car wheels had caved under the cars and locomotive.

Every wheel they saw was cracked and flawed and broken like brittle glass that has been dropped on hard tile. The wheels had simply pounded to pieces under the speeding train, dropping cars and engine and all to slide wheelless along the track till the snout of the locomotive caught in the ties and telescoped the whole mess together.

CHAPTER XV

The Boss!

As Carlisle had said, he intended to ride with the girls on the train to the last stop before Ludlow. Nellie and Rosabel saw, as the train slowed for that stop, that it was a small depot unused and shut up during most of the day. The name of it was Larchgrow, and there wasn’t a house or building of any sort in sight of it over the sandy dunes.

“We get off here,” Carlisle said softly, as the train slowed. “You go first. Get up and walk ahead of me to the vestibule of the car. Take your bags with you so it’ll look natural.”

On this, a commuters’ train, there was no porter. Nellie took her small bag from the rack, and Rosabel took the larger one they’d brought.

They walked down the aisle.

Behind them walked Carlisle, face pleasant and smiling. He had his newspaper rolled and in his right hand. He slapped it idly against his thigh as he walked. Had anyone stared closer he might have seen the gun in the inside of the roll. No one, however, stared at all.

The two girls got off. Carlisle followed and stood a few feet from them, smiling amiably. The train rolled off, gathering momentum swiftly.

Carlisle dropped the smile.

“O.K.,” he said. “Walk ahead of me to the road— Wait! Back behind the building!”

A car had appeared on the road, and Carlisle forced the two girls to hide behind the depot till it had passed. It went by in a hurry. And then Nellie and Rosabel heard the sound that had sent Mac and Smitty, in that car, ahead so fast to try to catch up with the train.

The eerie noise from the sky.

Carlisle, blond and sleek and well-groomed as any prominent young clubman, smiled at the sound. But Nellie Gray and Rosabel stared at each other in dawning horror.

“The train!” gasped Nellie. She stared at Carlisle.

“Is that noise—does that mean—is the train going to be wrecked?”

“Probably,” said Carlisle, as indifferent about it as though discussing the weather.

“You’ll pay for these things! You’ll all pay!”

“Oh, come now,” said Carlisle affably. “I think it was very considerate of the boss not to come around while we were on the train. Don’t you?”

“The boss?” Nellie echoed him. “What unspeakable person is behind this? Or—is it you?”

“You flatter me,” said Carlisle. He prodded the two ahead of him, toward the road, distant here. “I haven’t the money it takes to hatch up a scheme like this. No, I’m not the one. But you know who the one is. You’ve all been fluttering him for forty-eight hours.”

“You mean Vanderhold? Darcey? Colonel Ringset?”

“I don’t necessarily mean any one of the three,” said Carlisle.

“Who, then?”

“My dear young lady,” Carlisle said with ghastly pleasantry, “suppose you think that just possibly you might escape. So you want to get information from me first. You haven’t a chance of escaping. But on the million-to-one possibility that you might, I shall tell you—nothing.”

“How did you know we were to be on that train?” persisted Nellie. Rosabel was looking straight ahead as she walked, by Nellie’s side, in front of the man. She was looking like a very badly scared, utterly helpless Negress. And while she looked that way, she watched for the slightest opening to act against Carlisle.

“It was reasonable to suppose that some of you would ride the train, eventually, so I rode it, too, to pick up whichever of you should board it for points north. I’ve been going back and forth all day. And finally you two get aboard.”

They went in silence, then, the rest of the way to the road. There was nothing in sight when they got there.

Carlisle shouted, “Shad!”

There was the snarl of a starter not far away, and a car wobbled over the matted growth and bumps from behind a dune where it had stopped till the car bearing Mac and Smitty had gone by.

“In!” said Carlisle, nodding to the car.

There were two men in the driver’s compartment. They were tough-looking thugs whose grins were worse than threats.

Nellie and Rosabel got in the back. Carlisle piled in front with the other two. He rode there, turned around so that he could cover the girls at every instant. Not for a second was there a gun off them.

The car drove slowly, drifting along at about thirty miles an hour. And in the sky above them the eerie droning noise began to sound again. It settled down toward them, louder and louder, nearer and nearer—

In Ludlow, Mac and Smitty delivered three badly injured persons from the wreck to the emergency hospital. The rest were coming in farmers’ cars and ambulances.

For the moment there was nothing more Smitty and Mac could do to help, so they drove to the Ludlow Hotel, where Nellie and Rosabel were supposed to come from an afternoon train. Both men resolutely put from their minds a hideous thought.

Possibly the two girls had been on that train, in the wreck, and had been so hidden by debris that their bodies hadn’t emerged during the first rescue work.

“They’ll probably show up about six o’clock, on a train routed around that point on another track,” Smitty said firmly.

“Of course,” said Mac, a little too loudly. “In the meantime, we’ll wait in the lobby.”

Ludlow was not very big, but the hotel was large and elaborate. It was supported by resorters from the city who spent a week to a summer along the beach. The lobby was as full of plush as a big city hotel.

It was not very big, for the size of the hotel, however. Mac and Smitty, sitting not far from the door, could hear what went on at the clerk’s desk.

A man came in whom Nellie Gray would have recognized, though Mac and Smitty didn’t. He was about sixty, with clear, pinkish skin, and light, clear eyes.

He went to the desk, and the clerk there was very respectful indeed. He knew this man—as did most people all around that district.

“Yes, Mr. Darcey,” he said. “What can I do for you?”

Mac and Smitty stared swiftly at each other.

“Whoosh!” the Scot whispered. “Abel Darcey! President of Catawbi Railroad, and general big-shot. What’s he doin’ here in Ludlow?”

They soon found out. They heard Darcey say:

“I came in to inquire about a young friend of mine. That wreck down the line—I’m so afraid she was caught in it. She was coming here for a few weeks’ stay with her maid.”

“Her name, Mr. Darcey?”

“Gray. Miss Nellie Gray. She is blond, blue eyes, rather small.”

The clerk looked through the registration cards.

“There is no Miss Nellie Gray and maid registered,” he said. “And since I’ve been on the desk, no one of that description has come in. I’ve been on since eleven this morning, too.”

“How,” muttered Smitty fiercely, “did he know Nellie and Rosabel were coming here? Is there a dictaphone planted back at our hotel?”

“I think we’d better find out how the mon knows,” Mac said grimly.

“I’ll be back in a half-hour or so to inquire again,” the two heard the man at the desk say to the clerk.

Then, before Darcey could turn, they were on their feet and walking out of the hotel door. But they didn’t go far. Mac stood against the building wall to the right of the doorway, and the giant Smitty to the left.

Darcey stepped out—and they moved to each side of him.

“Just a minute, Mr. Darcey.”

Darcey stared up at Smitty’s moon-face, with eyes in it that were not quite so blandly harmless-looking as usual. Then he looked into Mac’s bleak blue eyes. His own eyes were apprehensive, but his face was admirably controlled.

“Well?” he said sharply. “I don’t believe I know you two men. Why are you approaching me?”

“We want you to take a little ride with us,” said Mac, nodding toward their rented car, parked nearby.

“Don’t be ridiculous,” snapped Darcey. “Naturally I wouldn’t get into a car with two strangers—”

His voice trailed to a halt as Smitty’s vast hand was laid very lightly, as if in affection, on his right shoulder. The hand was very near Darcey’s throat.

“I can break your neck,” said Smitty, smiling for the benefit of passers-by who were staring at him because of his great size, but who hadn’t any notion of what he was up to, “with one twist of my fingers. As fast a death as one from a bullet. I will break it, too, if you don’t stroll to the car with us.”

Darcey looked as if he were going to risk everything in a shout for help. He stared into Mac’s bitter blue eyes, then into Smitty’s lighter, china-blue ones—and didn’t yell.

“Where are you taking me?” he demanded, after getting in the car.

Mac, at the wheel, drove off without replying. Smitty, beside Darcey in the back seat, said, “Oh, not very far. Just out of town enough to be able to ask you a few questions without being interrupted.”

“What questions?”

“The most important is—how did you know Nellie Gray and Rosabel were due at the Ludlow Hotel?”

“Oh, that! Of course. You’re MacMurdie and Smith, aren’t you? I’m stupid, not to have recognized you at once, from Benson’s description. But even after that, I wasn’t prepared for a man quite so big as you.”

His eyes went over Smitty’s giant frame.

And Smitty stared back with dawning dismay in his full-moon face.

“Benson?” he said, in a different tone. “He told you the girls were coming to Ludlow? And he said we were coming, too, and described us?”

“That’s right,” Darcey nodded.

“Watch yersel’,” Mac burred, not taking his eyes from the road. The car was at the town limit, now, and rolling into the open dunes country. “The mon may be puttin’ on an act.”

“An act?” Darcey repeated. “I don’t understand.”

“Why would Mr. Benson tell you any of our plans?” Smitty demanded.

“Your employer,” said Darcey, “seemed to think my life was in danger. So he called on me.”

The car rounded a bend in the road. Ahead a few hundred yards was a lane going into the scrubby but thick woods growth typical of spots of the dune country.

“Would you mind turning around and driving me back to town?” said Darcey politely.

“I’ll tell you on the way,” he added.

Mac rather mechanically turned into the lane to back around in the road. Then he stopped the car, nose in the trees.

“We’ll not be goin’ back,” he said, “till ye do some explainin’—”

The Scot stopped, exclaimed aloud, and tried frantically to back out. But it was too late, then!

A man had stepped from the thick growth to the right. He had a submachine gun in his hands. Another man, similarly armed, appeared on the left side of the car. And two more stood, as though risen from the ground, directly in front.

Mac stopped trying to get away. They weren’t in one of The Avenger’s special bullet-proofed cars. They were in this rented thing that could be riddled by bullets like a tin can.

“Ye double-crossin’ devil,” Mac grated, glaring at Darcey.

The railroad man’s face remained inscrutable. Only his eyes showed a humorless smile. He didn’t even answer. He got out of the car and greeted a fifth man, who appeared at that moment with an automatic rather negligently hanging in his right hand.

The man was the ubiquitous Carlisle.

“Well, boss!” Carlisle said, mild surprise in his smooth face. “I didn’t quite expect to see you show yourself openly to us all, no matter what the occasion.”

“It’s quite safe now,” Darcey said to Carlisle. “No one here can ever say anything without sending himself to the chair. And with the capture of these two,”—he stared at Mac and the giant, who both trembled with impotent fury—“our roundup is practically complete. When we get the altruistic gentleman at the head of things who calls himself The Avenger, we’ll be through. And I have an idea he is on his way up to our headquarters right now, thinking himself very safe indeed.”

CHAPTER XVI

Invention—A Crook’s Tool!

Dick Benson had guessed the ferry’s new location right on the nose.

The big scow had been towed north, to a point a little above Ludlow where scrubby woods bordered the lake for several miles. There, it had been beached in a small cove. Branches had been cut and strewn on its top so that a cursory search from the air would not have revealed it.

The giant thing was sure to be located in a few days; but the gang using it had every reason to expect that it wouldn’t be found till after they were through with it.

The ferry’s hold was brilliantly lighted by the electric plant run by the diesel. You could see the drums of oil and aviation gasoline, and the small machine shop, and the mysterious vats of water quite plainly. Also, you could see something else, the like of which had never been seen before.

An airplane. But a plane like something out of the book of tomorrow.

It was a big single-motor, cabin job, with conventional lines. But it wasn’t the design that caught and held your eye. It was the material from which it was built.

The plane seemed to be made of glass.

Wings were transparent, fuselage was transparent, seats and pontoons and struts were transparent. It glittered in the improvised hangar like a gigantic dragonfly. Or like a bird of crystal.

The only thing that bulked solid and heavy through the crystalline casing was the motor itself.

Along one wall, staring with fascinated eyes at the plane, were all of Dick Benson’s aides. For once, it looked as if The Avenger had been beaten. Only the pale-eyed man with the prematurely white hair, himself, was not yet in the net.

The giant Smitty leaned his vast back against the timbers of the ferry’s side. He was bound again, with as many coils of rope as would be used to tie an elephant.

Next to Smitty was MacMurdie, burring threats under his breath against the gang who were busying themselves with the plane. Next to him was Josh, who even at such a moment was looking sleepy and thick-witted, and seemed annoyed only at the discomfort of his bonds.

Beside Josh was Rosabel, seeming to be a very frightened Negress. Then came Nellie, helpless and small and appealing-looking—but dangerous as a stick of dynamite if she ever got a chance to act.

The whole bunch of them—helplessly bound—with the gang triumphant.

And there, talking to Carlisle, was the hitherto unsuspected head of the gang, himself: Abel Darcey. That was what infuriated the two girls and Mac and Smitty and Josh more than anything else.

The leader, himself, within a few feet of them, and they could do nothing to scotch him!

Sleek, blond Carlisle was arguing for haste.

“This car ferry’s going to be found very soon. Benson must have reported how it’s being used, and the cops will be hunting it. We’ve got to get through and get away before it is spotted.”

Abel Darcey nodded his distinguished-looking head. It was with a shock that you looked at that fine figure of a man and realized the deviltry he had planned.

“You can rest your mind about the time element,” the five trussed aides of The Avenger heard Darcey say. “We are almost through. In fact, when we leave here in a few hours, we will leave for the last time.”

Carlisle’s sleek brows went up.

“We have done enough to the railroad,” said Darcey. “That one last wreck will break it. The stockholders will rush to sell, at a bargain figure, and so the road becomes mine.”

“But the rest?” said Carlisle.

“We have built up the ‘foreign-invasion’ myth almost enough. We will topple one more building. Then there won’t need to be any more catastrophes. The story about invasion by a secret enemy will slowly die. But not for a good many years will any steel but Catawbi steel be used for building purposes in the Middle West. People won’t have any other metal but that which stood up in the collapses.”

“You’ll get hundreds of millions out of it,” Carlisle said, a little resentfully.

“You, and all the rest, will be rich beyond your dreams,” Darcey retorted coldly. “You have no complaint to make.”

“Oh, no, not at all,” Carlisle’s voice was hurried. It was evident that he didn’t want to irritate this man.

Darcey’s eyes swept over the bound figures propped against the side of the ferry.

“These people have been annoying,” he said. “But they won’t bother us any more!”

“This plane, boss. What’ll we do with her after tonight?”

Darcey’s eyes ranged over the glittering ship.

“We will take her out to the middle of the lake and sink her, of course. Along with the little device that has been such an important cargo. The plane, and that invention of the Gants, are the only direct clues against us. So we shall destroy them.”

“Seems a shame to sink that plane,” said Carlisle.

“It would be more of a shame to have it found—and traced to me! Are the men ready to prepare it for this evening’s work? All right. Have them go ahead, then.”

The gang had been swarming over wings and fuselage like ants over a bit of bread. Their swarming began to have more purpose now.

They had been loosening kingbolts and struts. Now they began taking the ship deftly apart.

The light hand-cranes were wheeled to the plane. The hooks were lowered to the left wing, raised, and the wing came off. The right wing was removed.

Men inside were taking out the seats—everything movable. The pontoons were taken off. In a little while the ship was dismantled and lay all over the ferry floor.

And then began a process that seemed insane.

The men, working like beavers, began dipping the parts of the plane, piece by piece into the great shallow vats of water.

First, one would dip into the drum that Smitty had discovered held the whitish, lardy-looking substance. He would get a piece as big as a walnut, and throw it into the vat being used. Then the crew would lower wing, or fuselage, or seats. The lowered part would be raised, dripping, and the process would be repeated.

It seemed a mad, reasonless thing to do. But as the process went on, and part after part was dipped time and again, the purpose of it became apparent.

With every dipping, the part in question became less easily seen. It became more invisible.

Mac gasped, as the key to the whole performance came home to his chemist’s brain at last.

“Of course!” he muttered. “The letters on the drum . . . IUM . . EARA . . And the little strip of Glassite that Rosabel told of being delivered to the Gant brothers’ laboratory! Of course!”

“What are you mumbling about?” said Smitty.

“The reason for this dippin’!” Mac said. “The chief’s known from the start. Of course! He must have known the minute you told of that drum of whitish stuff with those letters on the side that hadn’t been quite scratched off! And I was too dumb to tumble to it.”

“You’re dumb, all right,” grated the giant. “I won’t argue with you there. But what—”

The parts of the plane had been dipped perhaps thirty times by now. And they had all become utterly transparent.

The word, transparent, is loosely used. Actually, nothing is absolutely transparent. Not even glass.

It isn’t generally realized, simply because most people don’t think about the matter much—but an object that is completely transparent would be completely invisible.

This plane, for instance.

It seemed to be made of glass. And at first thought, you’d get the idea that a glass airplane wouldn’t be seen in the sky because you could look right through it and see the clouds on the other side. But it wouldn’t work out that way.

Glass is fairly transparent, but its reflective powers are bad. Or, rather, too good. Every ray of light striking glass at an angle is reflected. So a glass plane in the sky would be as plainly seen as any other ship. More plainly, perhaps: every polished surface on it would constantly be reflecting sunlight till the thing hung like a glittering diamond in the heavens.

But the dipping process to which the glassy substance of the plane was being subjected was taking away its reflective powers!

Part after part, as it emerged from trip after trip into a vat, with the whitish stuff being put in first, was being rendered more and more truly invisible. That is—it transmitted all light, instead of giving its presence away by reflecting some of it.

Finally they were done. And a miracle had been accomplished.

Smitty and Mac stared with bulging eyes while men carried the fuselage back to the center of the hangar. They seemed to be laboring along under nothing but thin air.

They caught up a wing and bolted it into place. They seemed to be kneeling in empty air, working with nothing.

Finally the plane was assembled again.

Faintly, very faintly, because of a few metal bolts and clips where strength needed good chrome steel, you could see a plane there. But the only thing you could really see was the motor, big and solid and prosaic in the almost invisible nose.

“The skywalker!” whispered Mac.

“Huh?” said Smitty.

“When that thing’s a mile or more up,” Mac explained, “all that could be seen would be the motor and the pilot. Two little dots in the air. Exceptionally good eyes could see the dots. An’ ’twould look like a man walkin’ in thin air, an eighth of a mile to a stride, an’ pushin’ somethin’ like a barrel—the motor—ahead of him. So we were told there was a man ‘walkin’ in the sky.’ ”

“Yeah, sure,” said Smitty. “I can see that, all right. But how do they do this?”

“Barium stearate,” said Mac. “That’s the whitish, fatty stuff in the metal drum. For some time now, a few chemists have known what barium stearate does to glass.

“Ye put a little barium stearate into plain water. It spreads into a film on the water so thin ye can’t see it. Ye dip glass into the pan. The barium stearate forms a transparent coating over the glass only a molecule in thickness. Ye do that thirty or forty times and ye have a shell over the glass about a millionth of an inch thick that makes it absolutely transparent—kills light reflection—an’ hence makes it invisible.”

“But that stuff can’t be glass,” argued Smitty. “You couldn’t make a plane out of glass. It’s too brittle.”

“Glassite,” Mac corrected him. “The stuff the Warwick Corporation has recently perfected. It’s as clear as glass, but as tough as steel. A brand-new plastic. That was one of the Gant brothers’ inventions: they found that ye can treat Glassite with barium stearate to make it invisible, just as ye can treat glass. Only ye can make things out of Glassite that you couldn’t out of ordinary glass. Like planes.”

“And the other invention of the Gant brothers?” said Smitty.

“It’s no doubt the thing that devil, Darcey, called ‘the little device that has been such an important cargo’ in the invisible plane. What that is, we can’t guess yet. But it’s somethin’ that can disintegrate solid steel from a mile or two up in the air.”

They stared for a moment more at the plane—wings, fuselage, pontoons, even seats, made of the stuff that had been rendered almost invisible by the barium stearate.

Then their eyes swung suddenly toward the lake end of the hangar. Toward the broken plank there that made such an innocent-looking small door.

The eyes of the gang swung that way, too. And then they were jumping around like a bunch of startled fawns, with guns in their hands that they obviously hated to use for fear the shots would be heard on some distant farm and the new location of the ferry prematurely discovered.

A man was coming in the door, dripping, of course, because you had to swim to get to it from shore.

He was an elderly man, with thin gray hair and a pinkish face, drawn now from fear and rage. His expensive clothes were ripped from passage through the underbrush around the beached ferry. There were bruises and blood on his face.

“Carlisle!” he yelled. “Hold that man calling himself Darcey! Get him—I say!”

The gang gaped at each other. And Smitty and Mac and Josh and the two girls stared with dawning amazement at the man who had been talking to Carlisle.

That man bent like a flash, straightened. There was a flick of his arm, and something thudded lightly into the timbers between Rosabel and Nellie Gray’s bound figures.

Then the man with the bruised face rushed from the door.

CHAPTER XVII

Twins—One Killer

The gang stared at those two with something like superstitious horror in their eyes.

One was scratched and bruised and dripping. He gesticulated excitedly. The other was immaculate and so calm that his face didn’t move a line.

But otherwise the two were as identical in appearance as any set of twins.

Both were elderly looking, of a size, with pinkish, clear skin and light-gray eyes. Both had thin gray hair. They were dressed the same.

There were two Abel Darceys in the ferry where there should only have been one. And the gang, seven men counting Carlisle, glared in stupefaction first at one and then the other.

“The chief!” breathed Smitty, tensing.

“Yes, but which one?” Mac breathed back.

The gang were wondering that, too.

“I told you to seize that man!” panted the Darcey who had just struggled into the ferry’s hull. He pointed at the calm and collected Darcey. “That man knows everything about us. Impersonating me, he entered my office and later my home, and went over every paper in both places. Then he came here, still impersonating me. Kill him or we’re all lost!”

“That’s the chief,” said Mac, nodding to the dripping Darcey. “Ye know his way. He never kills himself, he traps his crooks into killin’ each other or into bein’ killed by poetic justice.”

Carlisle started to swing his gun bewilderedly on the Darcey who had come in here with him.

“That’s the man to take,” the immaculate Darcey said, nodding toward the dripping one. “Don’t you see? He must be this man Benson. I’ve heard that he can make his face up to resemble anyone. He has come here to try to rescue his associates, and is trying it in this way. Tie him up. We’ve been waiting for just this visit from him—and now he’s here and he’s ours. He wasn’t as smart as he thought.”

Two of the gang laid uncertain hands on the dripping Darcey, who began to act a little like a maniac.

“You fools! He’s the one! He waylaid me in my car just outside Gary, and left me tied in an old shed. I got loose and came here to warn you, and to get him. I tell you he went through my private documents.”

For a moment Carlisle was convinced. Also, he was murderously angry.

“You mean to say you—if you are Darcey—left papers around that would tie us in with the wrecks and building collapses?”

“No! Certainly not! There’s nothing to carry weight in a law court. But he knows the whole thing now, even if he couldn’t prove it. And he could prove it if he got away with that plane and the little destructive engine aboard it. Kill him, I say!”

The calm Benson stared coldly at the excited one, who glared back with maniacal hate.

Carlisle spoke, after a little while. The sleek young man-about-crime had a head on him.

“This is getting us no place,” he said. “One of you is Darcey, one of you isn’t. What we want to do is find out which is which. It wouldn’t do much good to search you both—I suppose each of you has some sort of identification papers, either real or faked. But there must be some way to tell the difference.”

“You might pull our hair and see if one of us is wearing a wig,” said the immaculate Darcey ironically.

The dripping Darcey suddenly calmed down.

“There is a way,” he said, with a dangerous new note of confidence in his voice.

Carlisle stared cautiously at him.

“As soon as we learned Benson was fighting us,” the man went on, “we set out to find as much as we could about him, didn’t we?”

“Yes,” nodded Carlisle.

“Well, we learned that he had gone white-haired overnight because of a shock. And we learned also that the same shock had paralyzed his face. It is because the flesh of his face is dead, and stays wherever his fingers put it, that he can mold his features to resemble any other man. It’s that paralysis that makes him a man of a thousand faces, as they call him.”

“But his face,” the dripping Darcey pointed out, “can’t move of its own volition. It’s paralyzed. Now—the one of us who can make his features move—smile, frown, anything—will be the real Abel Darcey. The other, who can’t—will have to die.”

There was silence in the big hangar. And the five leaning bound against the side wall felt their flesh creep in that silence.

“As you can see,” said the man who had just come into the hangar, “I can move the muscles of my face.” He grimaced, wrinkled nose and forehead.

Almost holding their breaths, all turned from him to the figure of Darcey standing calm and cool a little to one side.

“All right,” said Carlisle. “Now move your face.”

The features of the immaculate Darcey remained immobile.

“You’re being a little ridiculous, I think,” came his calm, cold voice.

“Yes?” Carlisle said softly. “Well, I don’t think so. Go on! Grin, scowl, whatever you like.”

The silence seemed to build up on itself in the hangar like a set of building blocks. Then one of the gang yelled:

“That must be Benson! Jump him!”

At least five leaped for the man who had come here first as Darcey. But in the moment of their leaping—he was no longer there.

If the gang had had any doubt as to his identity before, they’d have had none now. Only one man alive could move that fast, and that was The Avenger.

With the five men knocking into each other in their murderous eagerness, the man with Darcey’s face eluded their reaching hands with lightning quickness, and flashed behind one of the big vats.

Shots came from behind the vat. They were whispering, sibilant spatts of sound, as Mike, Benson’s special .22, spoke from its silenced little muzzle.

A man fell with a gash on the exact top of his head where the bullet had ceased him into unconsciousness. Another howled and clutched his shoulder. But the rest got around the vat, and found their quarry gone, shadowlike, again.

The next glimpse they had of him was on the plane.

They saw his body through the transparent substance, saw him climb a wing that seemed nonexistent, and enter the fuselage.

“If he starts that motor—” screamed the real Darcey.

“He can’t get away in the plane,” snapped Carlisle. “He can’t get the doors open as long as we have the controls, out here.”

“He could bang the plane forward, smash it up!”

“Not without gas, he can’t,” said Carlisle coldly.

Smitty literally groaned, at that. Benson’s move had been so beautifully swift and well-timed that it certainly deserved success. But it wasn’t going to succeed with empty Glassite gas tanks in the plane!

Four of the gang were in the fuselage now. They jumped for the man at the controls.

Benson’s aides, through the side of the fuselage, saw their chief’s hands whip to his eyes swiftly. They knew why. Over his eyeballs he had cupped thin glass lenses, of the color of Abel Darcey’s eyes, when he made up to resemble the man. Those could be broken in a fight and could blind The Avenger. So he took them out.

He turned just in time to meet his leaping attackers.

Four against one. And that one was only an average-sized man, five feet eight or so, and certainly weighing no more than a hundred and sixty pounds. But in Benson’s unspectacular body there was a muscular power almost as great as that which the giant Smitty, himself packed in his vast frame. And there was more than Smitty’s speed and deftness.

The first man went flying over Benson’s suddenly crouching form, to bang headfirst against an almost unseen control board.

The second and third found themselves tripping together and falling almost without knowing how it had happened. But the fourth got squarely on Benson’s back, in spite of The Avenger’s breathless speed of movement. And he managed to hold Benson till the other three could get up and join him.

One raised his clubbed gun and banged it down. Benson sagged a little. There was a second murderous blow. Benson fell to his knees, still fighting. One of the men hit him from behind.

“If I ever get my hands on them—” Mac groaned.

Benson went limp. His superhuman fight in the pilot’s cramped compartment was over, and he was beaten.

The four carried him out and dumped him next to their other captives.

The real Abel Darcey came over, and anxiously watched the men tie Benson, making sure he couldn’t possibly work loose.

“That was a narrow squeak,” Carlisle admitted. “The guy almost was too smart for us. But it’s all over now. Except our part of it. Still want to go through with that, boss? Still want to knock one more building down?”

“Of course,” said Darcey. It’s important to give the Middle West one more scare to think about. But even if I hadn’t planned to do it before, I’d do it now.”

He stared at Benson, rubbing his hands slowly and thoughtfully together.

“We have kept our skirts pretty clear through all of this,” he said to Carlisle. “Right now, save for this plane which was ordered in sections by men working for me, and the Gant destructor aboard, there is nothing to implicate any of us in the wrecks and collapses later. Just the same, it is well to make sure. And we’ll do it this way.

“We’ll leave these people tightly bound. We’ll set a slow fire that will destroy them and the ferry several hours after we’ve taken off and are safe, ourselves. We’ll plant the blueprints of the Gant destructor in one of the cars outside, together with some of Benson’s personal possessions.

“After the fire, there will be ample evidence in the debris to prove that it was from here that the invisible plane operated. Benson’s remains can be identified by dental and skeletal formation. The blueprints will prove that he was behind the plane’s destructive trips. Benson, it seems, is a man of some mystery, so the police will take the circumstantial evidence as gospel. Then, later, when it comes out that I benefit from what happened, no one will think to connect that fact with the crimes because the world will be sure Benson did it all.”

“Boss,” said Carlisle, almost humbly, “you’re good! I’ve said so from the start, and I say it again.”

He stepped to a small steel locker, and took from it a little roll of blueprints. He walked to the unconscious Benson, and pressed Benson’s hands to the blue paper in half a dozen places. The Avenger’s fingerprints were on record, of course, and these would doubly prove his original theft of the Gant brothers’ invention.

He handed the prints, and a gold pocketknife and the little .22, Mike, to one of the gang.

“Put this in the blue sedan. That’s the hot car. Then get in the other, the gray convertible, and drive back to Chicago and ditch it somewhere.”

The man left. Those in the ferry, dimly through the thick old hull, heard a starter sound out in a few minutes. The man was planting proof that Benson was to blame for the deaths and destruction, in the one car, and driving the other off to conceal it.

“Now the fire,” said Darcey.

“Easy,” said Carlisle. He pointed to the drums of aviation gasoline. “Those’ll make a fire like nobody’s business.”

“But we don’t want it that fast,” objected Darcey. “We don’t want the first to really start for at least two hours, so that when they start figuring it out later, Benson will have had time to crash this one last building and then return.”

“Rope,” said Carlisle, “makes a good slow fuse. I’ll soak fifty feet in gasoline, put one end in a half-empty gas drum, and light the other end when we leave. It’ll take about two hours for the rope to burn to the drum. Then we’ll have an explosion of flaming gas that’ll catch the whole ferry almost at the same minute. After that—zing.”

Carlisle had carefully poured some gasoline in an open pail. The fumes were acrid in the inclosed place. He set a coil of half-inch rope in the stuff to soak.

“Fuel the plane,” he called to the men. “Come on. Snap into it. This is the last job—then we’re all done—and all safe.”

CHAPTER XVIII

Backfire!

Fifteen minutes later, one of the men threw the switch that opened the hangar doors cut into the end of the ferry’s hull. The little motor moaned and the doors slowly opened. The man stopped the diesel motor, and the lights went out.

Through the big doorway came bright moonlight. This was the first time the strange plane had soared the skies save in sunny daylight. But so bright was the moon that the effect would be the same. You’d hear the weird droning sound in the sky—made by a motor a little higher speed than most and hence emitting an angrier, shriller snarl. You’d hear an eerie whistling—made by wind shrieking over wing surfaces when the planes motor was cut and she drifted down. You’d look up into a sky so moonlit that even a bird could be seen at a thousand yards.

And you’d see nothing.

There’d be half a dozen men, instead of just a pilot, to see, this time, along with the motor. But at a couple of miles you wouldn’t be able to pick them out.

Darcey got into the plane first. He seated himself, seeming to sit on moonbeams and nothing else. The rest of the men followed him. Carlisle was last.

Carlisle took a final look around, struck a match, and lit the end of the soaked rope. The other end dipped down into one of the several dozen gasoline drums. The improvised fuse sputtered a little, then took hold.

Only it burned faster than any candle wick.

Carlisle waved to the bound Avenger and his aides.

“So long,” he said. “How do you like your toasting? Brown, or black?”

The half-inch rope smoldered steadily, with the flame traveling toward the gas drum. The drum would act like a big bomb when the flame got inside. It would scatter burning gasoline to the farthest ends of the ferry.

“The one thing I couldn’t be sure of,” came a voice, “was that Darcey would get into the plane, too. But his anxiety to be sure the plane was later destroyed would guarantee that, of course. That hadn’t occurred to me.”

“Chief!” Smitty fairly yelled. “I thought you were still out. I was even afraid you were dead, after those clouts they gave you with their gun barrels.”

Benson stirred in his bonds and managed to sit straighter against the timbers. The dim light from the moon outside showed his set, dead face as a white blotch. The cold, colorless eyes in that face, like ice in a polar dawn, seemed to generate their own pale light. He was bound. Death seemed near—and inescapable! Yet never had he seemed more invincible, more awe inspiring. His paralyzed, emotionless face was like the grim, unyielding countenance of fate.

“You can roll to a blow so that you almost avoid it entirely and yet seem to take it,” he said, “if you’re expecting to be knocked out. And wanting to be.”

“You . . . . wanted to be knocked out?” gasped the giant.

“Yes,” said Benson, voice as cold and calm as his paralyzed face. “Nellie, can you make it?”

“In a little while,” came Nellie Gray’s voice.

“Whoosh!” cut in Mac. “What’s this all about? Ye didn’t really want to be captured, Muster Benson?”

“After I got here and saw how things were working out, yes,” said Benson. “Because it is up to us to make Darcey destroy himself, since legal justice can never reach him. He was making no idle boast when he said there were no loose ends to incriminate him in a court of law. That’s true. In all the things he has done, he has left no clue against himself.”

“But ye don’t know all the things he’s done—”

“We can guess them all save for a few details,” said The Avenger quietly.

“The Gant brothers discovered that Glassite would become as utterly transparent as glass when dipped in water filmed with barium stearate. They conceived the plane idea, to be used in wartime. An invisible plane would be handy. They also discovered some sort of vibrator, probably an oscillator-type with amplifier, that, when tuned to the exact chemical analysis of a substance, would destroy that substance. The blueprints Darcey was so kind as to leave in the car outside will give us the more precise details. But the disintegrator, set on steel, for example, would so disarrange the molecular structure that the steel would almost fall apart, like rotten punk. That would make buildings fall. If kept directed at steel long enough it would rearrange the molecules into the simplest of all forms, which is that of hydrogen. Thus solid steel would pass off as a gas—which is what happened to the railroad rails, and the nails and screws holding that depot together.

“The Gant brothers must have discovered that their inventions weren’t good for war. The barium stearate treatment was slow, and the microscopic film making the plastic invisible would only last a couple of hours. The treatment was wearing off a little when you and I saw the ‘ghost’ plane, Mac. Also, to destroy something, a bit of that substance had to be obtained beforehand and the vibrator tuned to its exact pitch. Impossible in war conditions.

“But Abel Darcey, friend of the Gants, saw in the two things the answer to an old dream of his. He, through his bank, really owned Catawbi Mines. Not Colonel Ringset. Darcey could foreclose any time he pleased. Now, if a sure market could be arranged for the inexhaustible Catawbi ore, and Darcey took it over, he’d soon become one of the richest men on earth.

“With the invisible plane and the disintegrator, he could enforce a market through fear— How about it, Nellie?”

“Almost,” Nellie’s strained voice.

“Darcey stole the inventions,” Benson went on. “Later, when the brothers tried to tell the police what had really happened when the pavilion collapsed, he decided they’d better die; so he had both brothers murdered. No loose ends there. And no loose ends later. So I went through his papers, impersonating him, and found plenty that proved to me that he was guilty, but nothing fit for a court—”

“How did ye know to impersonate Darcey to begin with?” said Mac.

“Because of the nails that had disappeared from the rubber heels of his shoes. Nellie reported that. When Darcey’s secretary saw them and took it upon herself to have the shoes repaired, she put the brand of Cain on Darcey’s forehead.”

“But I thought that only indicated his life was in danger—as the Gants’ lives were when the nails were taken from their shoes!”

“Not at all,” said Benson. “I’ve said the vibrator could destroy a given substance only when experiments had been made on a sample. Well, the Gants, in experimenting with the destructor in their laboratory, picked a steel with the same chemical analysis as their shoenails. So the nails were destroyed, too. Incidentally when the vibrator destroyed the pavilion, it hit a pitch for America Steel that also ruined a lot of glass with the same resonating pitch.

“However, Darcey, to destroy competing steel but not Catawbi steel with its trace of chromium, had to experiment with samples, too. He did it in his office late at night. The nails disappeared from his shoes, also. That report of Nellie’s told me instantly and finally who we were after. There was a slight chance that Ringset was also in on the plot, so I sent Josh for a last check-up on him.”

Mac was watching the slow creep of the flame along the rope toward the gas drum. But even that couldn’t kill his curiosity.

“So ye went to Darcey’s headquarters, made up as him, and searched his papers?”

“Yes,” nodded Benson. “And while I was there, some lieutenant phoned a report of Josh’s capture, and the rest of you would be taken soon. I left and started for Ludlow to help. I ran into Darcey on the way, tied him up as he said, and came on. I was going to the ferry, still as Darcey, after I’d found out whether or not the girls were safe at the hotel. But I tangled with you. Then, at the woods lane, I saw from a slight distance that there were armed men hiding. I thought my best way into the ferry would be as the leader who decoyed you to your capture. So I saw to it that we were taken.”

“And we were taken!” said the Scot bitterly. “The skurly succeeds. We’re helpless here, and he’s in the sky on his way to knock over another building.”

“We’re not so helpless, Mac,” said Benson. “Nellie—”

“Finished,” said Nellie, standing up and shedding rope loops. “I’ve hacked my wrists to bits, though.”

The thing that had thudded into the wood between her and Rosabel before Benson’s capture had been The Avenger’s throwing knife, Ike.

Nellie had been sawing awkwardly at her bonds ever since. Now she was free.

She cut the loops from around Benson. The gray fox of a man trod on the burning rope and extinguished the flame, then loosed Smitty and Mac, Rosabel and Josh.

“We’re all right,” said Josh in a troubled tone. “But down in Chicago some unnamed building will fall—”

“No,” said The Avenger. “It won’t.”

They stared at him.

“They have very carefully built up the fear, in Chicago, of invasion from the air by some secret enemy,” Benson explained. “They have gone to great lengths to build up that terror. And in doing so, they have gone to great lengths—to plot their own destruction.” He stood before them, tautly erect, not a big man, yet seeming to fill the place. His death-white face was turned toward the point in the horizon toward the plane had set her nose.

The gang stared out through the invisible cabin walls as the mystery plane soared, at nine thousand feet, over the twinkling lights of South Chicago. It was about ten, now. The lake was a sheet of silver in the moonlight.

The skywalker!

Only there were eight skywalkers, now. Carlisle, and Darcey, and six gunmen. Of the six, one had Mike’s .22 slug in his shoulder and was sweating and swearing with pain. Another was still unconscious from having been so expertly creased by Mike’s little leaden pea.

“Will a man be standing by in the cruiser in the center of the lake to pick us up after we land and sink the plane?” Darcey asked nervously.

“Of course,” said Carlisle.

The sleek young killer was composed. Darcey was not. This was his first time aboard the special craft that had, at his orders, flown and destroyed five times before. He was very nervous. Yet he’d had to stick with the plane till it was finally destroyed, for his own protection.

“What’s the building we get this time?” Carlisle said, as the plane droned over the southern part of Chicago proper, with the tall buildings of the Loop just ahead.

“The Insurance Exchange,” said Darcey, dabbing at his moist forehead. “That’s one of the buildings in which both Catawbi steel and regular steel were used. It will, once more, show the superiority of Catawbi metal.”

“How is it,” said Carlisle curiously, “that this little vibrating dingbat can pick ’em so fine? Steel’s steel, I should think. Why isn’t Catawbi steel disintegrated?”

“I don’t think even the Gant brothers quite knew,” Darcey said. “There is a slight trace of chromium in Catawbi ore, and that seems to make the metal respond to a little different pitch of the vibrator. That’s all they could say about it.”

“Whatever makes the difference, it’s lucky for us—” Carlisle started to say. Then he pointed through the cabin wall. “They’ve heard us down below. Look! Four army planes. That’s a laugh—to see ’em circling around hunting us, and not seeing us—when all the time we’re right under their noses.”

“It may be humorous to you, but I don’t like it,” Darcey said, wiping more moisture from his clammy forehead. “Here! Set the vibrator, direct it as the Insurance Exchange, and let’s get through and away.”

Carlisle had handled the little thing before. The second, and most revolutionary, of the Gant brothers’ discoveries.

There was a black metal case, looking about the size of a small portable radio. In one side there was a screened circle, like that which conceals a radio loudspeaker. Inside the case there was a maze of fine antennae and delicate diaphragms, and two amplifying tubes. The contraption was hooked to a small generator geared to the plane motor, and that was all Carlisle could tell you about it. Darcey always set the pitch of the thing before a job, after experimenting with whatever steel was to be knocked to bits.

The disintegrator was all set now. Carlisle aimed a long, narrow cone so that its point was directly on the big Insurance Exchange Building, and snapped the little switch. There was a soft hum, raising rapidly in tone till it tore at the eardrums, then going up beyond the range of audibility.

“Hey!” said one of the men suddenly. “Them Army planes! Looks like they were coming right for us. As if they could see us!”

“Nonsense,” said Darcey, voice shaking but sure. “We are invisible.”

Carlisle said, “We’ll cut the motor for a few minutes, though. After all we can be heard, if not seen.”

They were hearing the drone down in the city. Hundreds of thousands of people were staring skyward. They saw the Army planes, but that was all. And none of them accounted for the eerie droning.

People shook their fists at the sky in agonized but futile rage. The enemy up there! If only it could be seen—

“Boss,” said one of the men, voice uncertain, “those planes are still comin’ right for us, even with the motor cut off—”

“So careful, they were, to build up that horror of an enemy invasion,” Benson was saying as all of them went out of the ferry to the blue sedan so generously left for them by Darcey’s overplayed plotting. “So successful, that under cover, Chicago is almost in a state of military rule. There are nine anti-aircraft guns of the latest type concealed in strategic spots through the city. And there are four of the fastest army battle planes ready to take off the instant detectors hear the droning noise. All training their deadly forces on the sky, waiting for the skywalker.”

“But what good will that do,” said Mac gloomily, “if nobody can see the plane?” The dour Scot, freed from death, was his pessimistic self again, sure that everything would go dead wrong in this worst possible of worlds—

The Glassite plane had wheeled from the strangely purposeful drive of the four fast army ships. The vibrator cone was no longer centered on the doomed building because of the maneuver.

“Swing it back,” ordered Darcey.

“Something’s gone wrong,” retorted Carlisle, eyes narrowed and venomous instead of deceptively calm and sunny. He countermanded Darcey’s order to the pilot. “Beat it! Out over the lake. The hell with the Insurance Exchange.”

“Carlisle—I’m giving the orders around here—”

“Look!” screamed the man with the wounded shoulder suddenly, glaring with horror in his eyes at the cabin wall.

That wall was glistening a little with reflected moonlight.

“That stuff you dipped the plane into!” the man yelled—“something’s gone wrong with it!”

“If the plane couldn’t be seen,” The Avenger replied to Mac, “the guns and army planes would be useless, of course. But Darcey’s plane, you see, isn’t going to remain invisible.”

“The barium stearate—” began Mac.

“The barium stearate,” said Benson, paralyzed lips barely moving in his white, dead face, “is adulterated. There was a small can of aviation gasoline near that drum. Probably to prime the diesel generator when they wanted to start it. I poured it into the barium stearate. It’s highly volatile stuff. It permeated the contents of the drum in a few seconds. This time the coating on that plane will dry and crack off in about a third of the time it usually takes.”

The terrified men in the Glassite plane saw a red spot burst in the city below them, heard a boom an instant later, and then felt the ship bob and twist in a gigantic rush of air.

“They’re shooting at us. They can see us!”

Two more red spots bloomed like angry measles from the city below. The Glassite plane was uncontrollable now.

Every surface was reflecting moonlight. Like a great, sinister jewel, flashing in the sky, it rolled and twisted with the tearing shocks of the close-bursting anti-aircraft shells. There was one more boom. The tail of the ship wavered and dropped off.

Four angry screaming army planes rushed on the two big fragments, diving after them as they fell, with twin machine guns on each ship drilling the “enemy” with a hail of .50 caliber slugs.

The disintegrator fell into the lake, followed shortly by gleaming pieces of Glassite and figures that were as limp and shapeless-looking as scarecrows.

The Avenger was listening, head a little to one side. Anti-aircraft guns make a lot of noise, and noise is transmitted a long way over water. It was seventy miles in an air line to the city, slanting over the lake end.

But Benson heard, faintly, the roaring boom of the opening shot, then two more, then a fourth.

He nodded for Josh and Rosabel and Nellie, Mac and Smitty, to crowd into the blue sedan.

“It’s over! By their own plans, they destroyed themselves.”

The others were too awed by the lambent flame in his colorless eyes to speak. Again The Avenger, playing with shrewd murderers, as if they were chessmen, had maneuvered them into a position where they had brought down vengeance on their own heads.

Face white and dead, unable to express the glacial triumph steadily flaring in his terrible eyes, The Avenger drove back toward a city that had been saved from horror and death.

THE END

Table of Contents

CONTENTS

THE SKY WALKER

CHAPTER I The Noise From The Sky!

CHAPTER II The Avenger!

CHAPTER III Death Masks a Secret!

CHAPTER IV The Sky Walker!

CHAPTER V Trapped!

CHAPTER VI Trickery Succeeds!

CHAPTER VII Death—Odds-On Favorite!

CHAPTER VIII Cold Extra!

CHAPTER IX The Bears’ Den!

CHAPTER X The Flying Dutchman!

CHAPTER XI Strange Revelations!

CHAPTER XII Murder Stroke!

CHAPTER XIII No Sale—No Suspect

CHAPTER XIV Murder Rides The Rails!

CHAPTER XV The Boss!

CHAPTER XVI Invention—A Crook’s Tool!

CHAPTER XVII Twins—One Killer

CHAPTER XVIII Backfire!