As the confused sounds, the crash, the tramp of rushing feet, the excited men’s voices and Frank’s high-pitched tones came dimly to Tom’s ears, a deadly sickening fear swept over him. Had they escaped the men from the submarine only to fall into the clutches of their confederates?

He had been under a tremendous strain, he had been terribly frightened, his heart had been almost bursting with excitement and he had been under water for much longer than ever before. The combination was too much for him. His head swam, he reeled, swayed; fiery sparks and flashes seemed to dance before his eyes; he felt a numbness stealing over him. Wildly he clutched at the ladder in a last despairing effort and seemed sinking, slowly, softly into a vast billowy void.

He opened his eyes and uttered a surprised cry. He was lying on the floor of the laboratory and his father, anxious-eyed, was bending over him while close at hand were Frank, Henry and Rawlins. Beyond and as a confused mass Tom’s eyes saw blue-clad figures and with a start he rose to a sitting posture.

“Gosh!” he exclaimed, staring about and for the moment not comprehending. “What’s the matter, Dad? What’s happened?”

“Are you all right, Tom?” asked Mr. Pauling. “We got you just in time. You fainted just as you reached the ladder top. Don’t you remember?”

Tom’s senses had now fully returned.

“Yes, Dad,” he replied. “I do now. Did Mr. Rawlins tell you about it? Gee! We did have a time! Are those men here?”

“Safe and sound, Tom!” Mr. Henderson’s voice assured him. “That is, one of ’em is. The other’s in bad shape.”

“Yes, Rawlins told us something of what happened,” put in his father as Tom rose unsteadily to his feet. “Look out, Son! You’re weak yet. Sit down or you’ll go off again.”

Leaning on his father’s arm, Tom staggered to the proffered chair and dropped weakly into it. Then he gazed about the room and at the crowd of men within it.

His father and Mr. Henderson, Rawlins, Frank and Henry were there. Near-by, was a strange, heavy-jawed man and beyond, near the door, were half a dozen policemen. But where were the two divers they had captured under the river? Then Tom saw that a heavily built, tow-headed man stood between two of the blue coats, his hands manacled and a sullen glare in his piglike eyes while, half hidden beyond two stooping men, was a form stretched upon the floor. But before he could form a question his father was giving quick sharp orders to the men.

“Get the Navy Yard!” he commanded, and as the heavy-jawed man jumped to the telephone, he snapped out: “Tell the commandant that Pauling’s speaking.” Then, before the operator had even asked the number, Mr. Pauling was uttering commands to the police. “Leave a couple of men here to guard the prisoners and get over to that block quick as you can. Get all available men you can pick up. Draw a cordon around it and don’t let any one in or out. Take my car! It’s up to you fellows to nab this bunch—if they haven’t got wise. On the jump now, Reilly! Take every one and everything that seems suspicious! Get me?”

Even before his last word rang out the policemen were hurrying towards the street, and an instant later, Tom heard the roar of their motor and the clang of their bell as the patrol dashed off.

“Navy Yard on the wire!” announced the man at the phone and Mr. Pauling grabbed the receiver.

“This is Pauling!” he announced shortly. “That you, Admiral? All right! Got important matter.”

Then, to Tom’s amazement, his father broke into the most utter gibberish, calling out a confused but rapid list of figures and words.

“That’s done!” he exclaimed, as he slammed back the receiver and turned towards Tom. “There’ll be a dozen destroyers and chasers combing the sea for that sub within fifteen minutes.” Then, with a different note in his voice, he asked, “Do you feel all right, Son?”

As Tom answered, his father turned towards the men bending above the figure on the floor. “Come here when you have a chance, Doctor,” he called. “Want you to have a look at my boy.”

At his words, one of the men rose and hurried to Tom’s side.

“Had a close call, my boy!” he exclaimed, as he took Tom’s wrist and drew out his watch. “Good thing Rawlins fixed up these suits so you couldn’t inhale flames. Different case with that chap yonder. He’s in bad shape. Trying to fix him up to get him to hospital. Afraid there’s no hope for him though! Oh, you’re O. K. Fit as a fiddle! Pulse fine! Nothing wrong with him, Pauling. Just a bit of nerves, I expect, and strain of being down too long.”

Hurrying from Tom’s side he again devoted himself to the injured man.

Things were moving so rapidly that Tom was dazed and was striving his best to gather his wits together and to understand all that was taking place. Mr. Henderson and Rawlins were talking earnestly in low tones, but Tom could not hear a word they said and was busy replying to his father’s, Henry’s and Frank’s questions and plying them with queries in turn.

Presently Rawlins and Mr. Henderson rose and as the former came to Tom’s side the other strode across the room and, facing the prisoner, stared fixedly into his face.

“I guess you’re all right, Tom,” said Rawlins, the tone of his voice betraying far more solicitude than was conveyed by his words. “You’re some kid, I’ll tell the world! You’ll be famous if you don’t watch out. Say, old man, I’m mighty sorry I kept you down so long. Never thought about you not being accustomed to it. I was so darned interested in that sub and those men I forgot about the danger to you, Tom. And say, Mr. Henderson thinks we’ve made some haul! I’ve been telling him the whole yarn—the Dutch talk and all the rest. Henderson thinks he recognizes that Hun we brought up and sees a big plot behind all this. Too bad the other fellow got flames and can’t talk. Your radio’s all to the mustard, I’ll say!”

At this moment Mr. Henderson’s voice interrupted them. As he had stared searchingly but silently at the prisoner the latter’s shifty eyes had fallen and he shuffled his feet uneasily. Then, without warning and so suddenly Tom and the others jumped, Henderson snapped out:

“Open your mouth!”

So unexpected was the command that the prisoner, long trained to instant and implicit obedience to orders, involuntarily threw back his head opened his enormous mouth.

“Thought so!” ejaculated Mr. Henderson and then, even before the surprised man’s jaws closed, he yanked aside the fellow’s denim shirt exposing the hairy freckled chest with a livid white scar diagonally across it.

“That’s enough!” snapped out Mr. Henderson. Then, addressing Tom’s father he remarked, “It’s he, Pauling. No question of it. Good day’s work this—thanks to Rawlins’ suits and Tom’s under-sea radio.”

“Wha-what’s it all about?” demanded Tom, absolutely at a loss to grasp the meaning of all the orders, the strange telephone message and Mr. Henderson’s statements. “Who are the men and what were they doing?”

“Never mind now,” replied his father. “We’ll get home first. Feel ready to go?”

“Oh, I’m all right now,” declared Tom. “Only a bit tired out.”

“Call for a couple of plain-clothes men to stay here,” Mr. Pauling ordered, turning towards the heavy-jawed man. “Don’t want any one meddling with the instruments. Keep that trap shut and bolted and don’t sleep on the job.”

Then, to the surgeons, “Soon as he comes to and can talk, call me up. If he says anything, write it down. Don’t let any one—any one, mind you—speak with him.”

The surgeon nodded in assent and as the other man again went to the telephone Mr. Pauling and Rawlins half lifted Tom, and, accompanied by Frank, Henry and Mr. Henderson, the party left the workshop. Already the two policemen had left with their prisoner and were pressing through a curious crowd which had gathered outside and which was held in check by more stalwart, blue-coated men.

“Gosh! you’ve got the whole of the New York police here!” exclaimed Tom.

“Not quite that,” laughed his father, “but Henderson surely did call enough of them. Guess they thought we were going to raid a liner.”

“Well, you didn’t name any limit,” replied Mr. Henderson chuckling. “You said ‘call the police’ and I called ’em. Might as well be on the safe side, you know.”

As Mr. Pauling helped Tom into Mr. Henderson’s car he saw the man whom Rawlins had captured in his spectacular battle under the river being shoved into a patrol wagon.

“Do tell me who he is,” begged Tom. “Is he a German spy?”

His father laughed. “You’ve forgotten the war’s over and done with and there are no spies,” he replied. “No, my boy, he’s not even a German. But you’ll have to wait a bit before I can tell you anything more.”

“Well, where did you send those policemen, then?” asked Tom. “You can tell me that.”

Mr. Pauling’s eyes twinkled. “They’ve gone to get your phantom radio man,” he replied. “Henderson’s men couldn’t find him before, but I’ll wager we located him this time. You see, Reilly happened to know about that old sewer and he says it runs under the block where you located the sender of those odd messages. Henderson thinks if he finds one he’ll find the other. We’ll run around past there and see if anything is happening.”

As Frank and Henry crowded into the little car, the boys saw a stretcher bearing a shrouded form being carried from their workshop to an ambulance, and the next moment they were moving slowly through the crowd which reluctantly made way before the insistent screams of the horn.

Close behind them came another car with Mr. Henderson and Rawlins and a moment later they were through the crowd and speeding towards the block to which Mr. Pauling had dispatched the police.

As they swung around a corner they saw a surging, densely packed throng blocking the street, while from beyond came the sounds of shouts and cries. Above the heads of the people the boys could see the glaring brass and shining paint of two patrol cars and, moving here and there, rising and falling as if tossed about upon a troubled sea, the low-visored, flat-topped caps of policemen.

“Can’t get through there!” declared Mr. Pauling, as his horn screeched and fell on unheeding ears. “Looks like a riot!”

Mr. Henderson had leaped from his car and was beside them. “Guess the men found something,” he remarked. “I’ll push through and see what’s up.”

With Rawlins by his side, he wedged his way into the crowd and the two were instantly swallowed up. But a moment later they reappeared, hats and collars awry, coats torn open, and panting.

“Whew!” exclaimed Mr. Henderson. “Might as well try to get through a solid wall. Hello! There’s another wagon!”

As he spoke, a bell clanged harshly and above the heads of the mob a car crowded with police could be seen forcing its way towards the center of the disturbance which appeared to be a large garage.

At this moment a huge, lumbering motor truck crept slowly from the garage door and an angry bellow rose from the crowd. But even an East Side mob must give way before a five-ton truck and the crowd, surging back to make way for the truck, swept around the boys and the two cars and engulfed them like a sea of rough clothes and angry, grimy faces.

“How the dickens can we get clear now!” exclaimed Mr. Henderson, as to save themselves from being knocked down and trampled underfoot he and Rawlins leaped upon the running boards and flattened themselves against the body of the car.

“Expect we’ll have to stick here until the crowd leaves,” replied Mr. Pauling, and added, “Unless they pick us up car and all and carry us out.”

Now the crowd was surging still farther back as though pressed by an irresistible force and above the bellowing, moving, multicolored wave of human heads and shoulders appeared a half-dozen mounted police, their well-trained horses forcing back the human wall which, despite jeers, taunts, threats and imprecations, gave way steadily before them.

As the police drew near and the crowd thinned out, one of the officers caught sight of the two cars and their occupants.

“Here you!” he shouted, urging his horse towards the car. “Get them flivvers out o’ here! Right about now and move lively!”

Mr. Pauling chuckled and Mr. Henderson grinned. “Show us how!” cried back Mr. Pauling.

“No sassing back there!” stormed the policeman now riding close. “Get a move on or I’ll pinch the bunch of ye for interferin’ with the police, resistin’ an officer and blockadin’ traffic. I’ll get enough charges against ye to send youse to the island for a year.”

Mr. Henderson and Tom’s father were shaking with laughter. “Don’t be foolish, officer. Don’t you see we can’t move?” Mr. Henderson asked.

The policeman’s face grew purple with anger and he pushed his mount close beside the car, calling to a fellow officer to help him.

Exasperated by the crowd, naturally quick-tempered and in a frenzy of rage at these “swells,” as he mentally dubbed them, defying his orders, he drew his club and raised it threateningly.

Mr. Henderson leaped from the running board to the policeman’s side and in tones which even the angry blue coat recognized as authoritative exclaimed,

“Here, that’s enough from you! You’ll find yourself broke if you don’t look out. Your job’s to protect citizens—not to abuse them!”

A look of mingled amazement and anger swept over the officer’s face.

“An’ who may youse be?” he began, hunching himself forward and shooting forth his pugnacious jaw.

Mr. Henderson stepped a bit closer and turned back the lapel of his vest.

The sudden change in the man’s attitude and expression caused the boys to burst out laughing. Surprise, incredulity, fear, and regret all spread over his big Hibernian features in turn. His half-raised arm dropped to his side, he seemed to shrivel and shrink in size, his pale blue eyes seemed about to pop from between his red-lashed lids.

Then Irish humor came to his rescue. Drawing himself stiffly up he saluted and with a twinkle in his eyes blurted out,

“B’gorra, Sir, ’tis sorry I am. But how was I to know, Sir? What with your kelly dinted in and your tie adrift and all. Sure I’ll see ye through here in a jiffy.”

The crowd had now been driven far back, and, escorted by the mounted men, the two cars proceeded slowly up the street until opposite the garage. A few idlers were still hovering about and were being chased away by blue coats, but inside the garage the boys could see a closely packed mass of men with policemen’s caps much in evidence, while the broad doorway was blocked by officers with drawn clubs.

As Mr. Pauling brought his car to a stop, a plain-clothes man pressed through the line of police and hurried to the car.

“What’s up?” demanded Mr. Pauling as the man came close. “Find anything?”

“Find anything!” repeated the other, his gimlet eyes fairly glistening with satisfaction. “You bet your—beg your pardon—I’ll say we did. Got the whole bunch—men, cars, booze an’ all. Want the story now?”

“No, don’t stop now, Murphy,” replied Mr. Pauling, “After everything’s cleaned up come around to the house and we’ll hear the whole yarn, the boys are entitled to know it. I’m expecting a call to the hospital at any time and must be on hand. Glad you got them.”

“I guess I’ll stay and see the fun,” said Rawlins, “that is, if I may.”

“Let Mr. Rawlins in, Murphy,” commanded Mr. Pauling. “He’s one of our crowd and all right. Wouldn’t have got this job over without his help. See you later.”

As the car drove off, the boys saw Rawlins pushing through the cordon of police by Murphy’s side and all three breathed a sigh of regret that they, too, could not remain to see what exciting and interesting things were taking place within the garage.

But they realized that it was no place for boys and, to tell the truth, all three were quite ready and willing to go home and have a chance to calm down and rest. Tom, of course, had been through a racking experience and was utterly exhausted nervously and physically, and Frank, who was younger and of a far more nervous temperament, had been so worried and frightened over Tom’s plight and the uncertainty of what was occurring under the water that he had become almost hysterical when it was all over. Even Henry had experienced enough excitement to last him for some time and boylike was crazy to rush home and tell his parents all about the remarkable adventures of the afternoon.

Leaving Henry at Gramercy Square, Mr. Pauling drove the car home while Mr. Henderson went to his office and Tom and Frank, who was staying at the Pauling home while his parents were in Europe, breathed a sigh of satisfaction when they found themselves once more in the cool, quiet interior of the house on Madison Avenue.