"Well, first, you know, Uncle Sam has some valuable seal islands in the Aleutian group. Maybe, during the war the j.a.ps or Russians have got careless about drifting around that way and carrying off a few hundred skins. Might be, you know.

"But I'm not saying that's it. A sub would be a mighty fine craft for watching that sort of game, though. And then, there's another thing I've thought of. There's gold in Russia, on the Kamchatkan peninsula; you know that, don't you?"

"No." Dave opened his eyes wide in surprise.

"Heaps of it. Tons and tons! Just waiting for the digging. And before we went into the war, when Russia was still with the Allies and needed money, our Government, or independent capitalists, I don't know which, furnished the Russians a lot of machinery for mining the gold; about a million dollars' worth, I guess. Then came the revolution in Russia. I doubt if a cent has been realized from the sale of machinery. Who's in possession of that peninsula at the present time? G.o.d alone knows. j.a.pan would like to meddle there, I'm sure. Perhaps we're being sent up there to conduct an investigation.

"Those are my two guesses. Take 'em for what they're worth."

"You don't think," said Dave, "that we'd attempt the Pole?"

The ensign was silent for a time. "No," he said at last, "I don't. Of course, Stefansson has said that a 'sub' is the most practical way to go there; that ice-floes are never more than ten feet thick and twenty-five miles wide, and all that; but there are too many unsettled problems relating to such a trip."

"But say!" exclaimed Dave, "who is this doctor of ours, anyway?"

"Blamed if I know," said Blake, as he turned away to go below.

"Well, anyhow," Dave remarked, "whoever he is, he's going to take us where the white ice-floes are drifting. Look at the color of this craft; blue-white, like the ice itself."

The journey North, save for a storm, which they avoided by submerging, was uneventful until they found themselves in the company of scattered ice-cakes with the snow-capped ridges of the Aleutian Islands looming up before them.

In no time at all every man on the craft realized that on these islands was to be found one of the objects of their quest; for, once they had sighted the sh.o.r.es, the funnel was dropped, electric power applied, and watchers, dressed in white to match the color of the craft, set to scan the sh.o.r.es for signs of life. They stole through the water like some ghost craft.

"Believe it's that seal-fishery business?" asked Dave, as he and the ensign took their watch.

"No."

Dave was certain from the tone that the doctor had confided his secret to the ensign. He asked no more questions.

So they drifted on. The wind had dropped. The swell rolled their craft as it plowed along. Here and there a sea-lion thrust its ugly head from the water. Twice a seal attempted to climb upon the slippery hull for a rest, but, to the amus.e.m.e.nt of the boys, slid back into the water. An offer to a.s.sist the third one was not appreciated, and the ridiculously human-like head disappeared beneath the water with great alacrity.

Dave had been searching the hills with his binoculars for some time when he suddenly gave the gla.s.s to the ensign.

"What's that tangle above the cliffs there?" he asked.

The ensign studied the cliffs for some time. Then he touched a b.u.t.ton with his foot and they turned silently sh.o.r.eward.

"That's it!" He said with an air of finality.

"What?" asked Dave eagerly.

"The wireless." Then the ensign explained to Dave the purpose of their journey. They had been sent into the Arctic to locate a wireless station, supposed to be placed in the Aleutian Islands; a station run by radical propagandists, part of a world-federation, which proposed to wreck all organized society. Had Dave realized that the missions of sub and airplane were alike he would have been startled. As it was, his face took on a tense, expectant look, his cheeks burned hot with excitement.

The Doctor was called to the conning-tower. After studying the contour of the island for some time, he said:

"Their shack, built of rocks and driftwood logs, is at the base of the cliff. That is good. We will divide into two parties. Four of us will go up the cliff and get above them, while four others will skirt the cliff and, under cover, await my signal. Our supporting party will take ropes, rifles and a machine-gun. I will go with the party to the top of the cliff. We will carry only rifles and some special instruments of attack which I have stored in canvas sacks below. Two men must remain on board.

Head in close to those rocks before us. They are out of sight of the shack and there is ice stranded there--a straggler will scarcely tell our craft from it. I have no doubt there are a number of them and that they are hardy ruffians. We must proceed with great care.

"Hark!" He put his hand to his ear. "They are sending messages now.

"In the future," continued the Doctor, as he handed Dave two strange-looking spheres, the size of a man's head, "the work of sheriffs, policemen and other officers of the law is not going to be quite so hazardous. When a criminal runs amuck, he will not kill a half-score of brave men before he is captured. The officers of the law will do what we will soon be doing, and a child can do the rest. Only," he continued, "watch your step going up that hill. It doesn't take much of a b.u.mp to get one of these funny little b.a.l.l.s excited."

Dave had been detailed to a.s.sist the Doctor. Ensign Blake would lead the supporting party around the cliff, there to await the Doctor's signals.

Besides the sack in which Dave carried the large spheres, there was another carried by a seaman. This one gave forth a metallic clinking, as if it were full of iron eggs. With the Doctor and the other seaman carrying two rifles each, the four men made their way slowly around the rocky hillside and were soon advancing silently, single-file, up the surface of one of those perpetual snow-banks for which the islands are noted.

The rocks above were much larger than they had seemed from the sub.

Twice, as he climbed over them, Dave's foot slipped and each time his heart was in his mouth. One stumbling misstep and all might be over for him. But he had the clear, cool head of a clean boy who had lived right, and an appreciation of the joy of living, which would take him far and keep him safe through many an adventure. So, safely, they reached the top of the cliff.

The Doctor motioned Dave to come back with him to a box-like edge of rock, which would give them a view of what lay some three hundred feet below. All was still. The moon, a great yellow ball, floated in the sky above and in the sea beneath. A lone sea-gull, awakened by the supporting party, sailed screaming away. Not a move, not a sound was to be detected below. Yet there, in a rocky cavern, were a number of world-criminals, and behind some crag were three jackies and their commander. Soon all this would be changed. Fighting, perhaps death, would end the quiet of that Arctic scene. Dave's hand trembled with excitement as he arranged the two sacks beside the Doctor. Even the Doctor's hand shook as he opened one sack and drew forth a number of small iron objects, the size and shape of a bicycle handle-bar grip. His face grew stern.

"Understand Mill's grenades?" he asked.

"Yes."

"All right. When I say 'Go' drop ten of these as fast as you can release the pins. Drop 'em on their shack."

Dave's heart thumped violently. He had thrown Mill's grenades at manikin "enemies," but never had he hurled them where human flesh was the target.

Slowly, mechanically, he arranged the ten grenades in a row.

"Go!" The word sang in his ears.

Ten seconds later from below came two sharp reports--his grenade and the Doctor's. They were off together. Crash followed crash in quick succession until the row was finished. Silence followed for a single second. Then came the cries and curses of men, as they staggered from their half-demolished shelter and began to scatter. Dave's heart thumped.

There were fifteen, at least.

"Now!" exclaimed the Doctor, and lifting one of the large spheres he dropped it over the ledge's edge. Just as that instance Dave saw one of the rascals raise his rifle and fire. Immediately there came a cry of distress. Dave thought he recognized the voice and a lump rose in his throat.

But now there came a dull m.u.f.fled explosion--the strange bomb. Instantly the men below began acting like madmen. Throwing away their rifles, they staggered about, tearing at their eyes, their throats, their clothing, and uttering wild cries of distress. At the same time three automatic pistols cracked, and Dave knew the doctor had given his signal.

To his surprise, he saw the three jackies emerge from hiding wearing gas masks. Quickly they overpowered the wild men, tied them and carried them around a point of land. As they did this the Doctor and his band kept guard above, rifles ready for any man who might, by some chance, recover sufficiently from the gas to shoot. But none did.

"It won't do them the least bit of harm," the Doctor said, as he noticed the look of surprise on Dave's face. "It's only chlorpicrin--a tear gas.

It comes in liquid form, so must be a.s.sociated with an explosive which transforms it into a gas and scatters it. You will see that our men are carrying them out of it as soon as they have them secured. It's a safe and harmless way of handling criminals. The war taught us that."

"But the ensign?" exclaimed Dave, as he saw the last ruffian in the hands of the jackies.

"Something must have happened to him," said the Doctor rising hastily.

"There was a shot," Dave reminded him.

Together they hastily made their way down the rough hillside. Slipping, sliding, falling, to rise again, they came to the lower surface and hurried around the point where the prisoners had been carried.

A strange scene awaited them. Sixteen men lying in a row, all tightly bound. And what a motley crew they were--j.a.ps, Russians, Mexicans, Greeks, and even Americans, they had gathered here for a common purpose.

But it is doubtful if one of them could have told what the next step would be, should their first task be accomplished.

Off to one side, lay Ensign Blake, white and still. One of the seamen was bending over him.

"Got an ugly one in the chest," he said simply. "Think we can save him?"