+ + +

It was Donald, the Wolf Scout, who saved the day for the prisoners of
the submarine.

As Barton rolled about whimpering and cursing by turns, he spied a
bright object protruding from the man's pocket.

"Is--is that the lever?" he asked, in tones that trembled with
excitement.

Mr. Barr darted on the object and pulled it out with a shout of triumph.

"Once more the Boy Scouts have saved the day!" he cried. "It is the
lever, sure enough!"

Close as the atmosphere of the cabin had by this time become, they all
found breath enough to give three ringing cheers. In the conning tower
Merritt, at the wheel, heard them, and guessed what they meant.

Fifteen minutes later the submarine was shooting upward to the surface
toward the blessed air. With what speed the hatch was opened when they
reached the surface and could inhale the pure ozone once more, may be
imagined. As soon as they had somewhat recovered a red light was shown
from the stern, and presently the _Viper_ came chugging up.

"Well, where in the world have you been?" asked Tubby.

"Where _under_ the world, you mean," laughed Merritt; "but for a time it
was no laughing matter, I assure you."

He then gave his fellow Scout a description of all they had undergone.
When the excitement was over, word was given to get under way once more,
and with the submarine leading, and the _Viper_ following the red light,
they held their courses toward the south.

It was dawn when they found themselves off a maze of small islands and
islets. Donald had the wheel, and was gazing ahead as the submarine, at
reduced speed, threaded her way among the shoals and sand bars.

All at once he saw something coming toward them that made his pulses
beat far above normal.

It was a green motor boat, with a single military mast and a high cabin.

He lost no time in notifying everybody, and the submarine decks were
soon crowded.

"Better get below, boys," warned the ensign; "that is undoubtedly the
rascals' boat. In fact, Merritt says he recognizes it. They are
desperate fellows, and when they see we have them cornered, they will
put up a fight. If they run, I mean to pursue them to the bitter end."

Reluctantly the boys went below, while the ensign and Mr. Barr stood on
the foredeck, revolvers in hand.

But although whoever was on the green boat must have seen them, the
craft came right on.

"Why, they actually mean to fight," gasped Mr. Barr.

"They're n