as he tuned his ears more acutely, he knew that it was the
squeaking of a hinge he had heard, and he felt sure it meant the opening
of a door near by.

Through the hole he looked at the door behind which was Levi Labenstein,
whether sleeping or preparing for some act which would put the ship in
peril and endanger the lives of all the passengers, could only be
guessed.

Then, as Blake watched, he saw the door open and the German come out.
Labenstein looked around with furtive glances, and they rested for some
little time on the door behind which Blake was watching. Then, as if
satisfied that all was quiet, the man stole silently along, the
corridor.

"Something doing," thought Blake. "Something doing, all right. He has
something in his hand--probably my flashlight. Much good may it do him!"

As Labenstein passed the stateroom where Lieutenant Secor was quartered,
that door opened softly, but not until the German was beyond it. And
then Blake saw the Frenchman peer out as though to make sure his
fellow-conspirator was fairly on his way. After that the lieutenant
himself emerged and softly followed the German.

"Both of 'em at it," mused Blake. "I'd better rouse Joe and let him keep
track of one, in case they should separate."

A touch on Joe Duncan's shoulder served to arouse him, though he was in
a deep sleep. He sat up, demanding:

"What is it? Are we torpedoed?"

"No, but we may be," was Blake's low answer. "Keep quiet and follow me.
Secor and Labenstein have both gone up on deck, I think. We'd better
follow."

"Shall we tell Charlie?" asked Joe, as he slid from his berth. Neither
he nor his chums had taken off their clothes.

"Yes, I guess we'd better get him up," Blake answered. "If you and I
have to watch these two fellows, we may need some one to send for help
in case anything happens. Come on, Macaroni," he added, leaning over
their helper and whispering in his ear. "Wake up!"

Charles was up in an instant, a bit confused at first, as one often is
when emerging from a heavy sleep, but he had his faculties with him
almost at once, and was ready for action.

"What is it?" he asked, in a whisper.

In like low tones Blake told him, and then the three boys, after making
sure by a cautious observation that neither of the suspected men was in
sight, went out into the corridor and to the deck.

It was quite dark, for all unnecessary lights were dimmed, but there was
a new moon, and the stars were bright,