“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 associated 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—­Japs, 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?”

The Doctor bent over, and tearing away Blake’s garments, made a thorough examination.

“He’ll pull through,” he said.  “But we must get him to the mission hospital at Unalaska at once.  Begin throwing those rascals aboard.  There’s a prison there for their accommodation.”

At that moment the two other jackies appeared, carrying a moaning burden in the shape of a Jap radical.

“One’s done in for good,” the foremost man explained.  “We searched the ruins.  Maybe we can save this fellow.”

“Take him aboard,” said the Doctor.  Then, turning, he directed the men who carried their fallen commander to the craft.

* * * * *

“Well, that about ends our present career in the Arctic.”  The Doctor was speaking to Dave, and emphasized his word with a sigh.  “I had hoped we might do something really big, but Blake will not be out again this season.  He’ll get around again all right, but it’s a slow process.”

Dave sat thinking.  Suddenly he jumped to his feet.

“Doctor,” he said eagerly, “there’s a gob on board who is sure a wonder at navigation.  Don’t you think—­think, he and I might manage the sub for you—­your trip?”

“H—­m.”  The Doctor grew thoughtful, but a flash of hope gleamed in his eye.

“Tell you what,” he said presently, “there’s a considerable ice-floe between the islands; the north wind brought it down last night.  Have your crew ready for a try-out in the morning.”

With a heart that ached from pure joy of anticipation, Dave hurried to an ancient sealer’s bunk-house where his men were housed.  “A try-out, try-out, try-out,” kept ringing in his ears.  What did it mean if they were successful?  Something big, wonderful, he was sure.  Russian gold?  Charting Northeast Passage?  North Pole?  He did not know, but nothing seemed too difficult for his daring young heart.