the _Jeanne_ resumed her way in the midst of the protecting
convoys, the value of which had been amply demonstrated. And when all
was once more quiet on board, Blake and his chums resumed their talk
about what was best to do regarding what they had observed just before
the setting off of the depth charge.

"I think we ought to tell the captain," said Charlie.

"So do I," added Joe.

"And I agree with the majority," said Blake. "Captain Merceau shall be
informed."

The commander was greatly astonished when told what the boys had seen.
He questioned them at length, and made sure there could have been no
mistake.

"And they gave a signal," mused the captain. "It hardly seems possible!"

"It was Labenstein who actually flashed the light," said Blake. "Do you
know anything about him, Captain Merceau?"

"Nothing more than that his papers, passport, and so on are in proper
shape. He is a citizen of your own country, and appeared to be all
right, or he would not have been permitted to take passage with us. I am
astounded!"

"What about the Frenchman?" asked Joe.

"Him I know," declared the captain. "Not well, but enough to say that I
would have ventured everything on his honor. It does not seem possible
that he can be a traitor!"

"And yet we saw him with the German while Labenstein was signaling the
submarine," added Blake.

"Yes, I suppose it must be so. I am sorry! It is a blot on the fair name
of France that one of her sons should so act! But we must be careful. It
is not absolute proof, yet. They could claim that they were only on deck
to smoke, or something like that. To insure punishment, we must have
absolute proof. I thank you young gentlemen. From now on these two shall
be under strict surveillance, and when we reach England I shall inform
the authorities. You have done your duty. I will now be responsible for
these men."

"That relieves us," said Blake. "We shan't stay in England long
ourselves, so if you want our testimony you'd better arrange to have it
taken soon after we land."

"I shall; and thank you! This is terrible!"

The boys realized that, as the captain had said, adequate proof would be
required to cause the arrest and conviction of the two plotters. While
it was morally certain that they had tried to bring about the successful
attack on the French steamer, a court would want undisputed evidence to
pronounce sentence, whether of death or imprisonment.

"I guess we'll have to leave it w