ith the captain," decided Blake. "We
can tell of his borrowing the light, and that we saw him flash it. Of
course he can say we saw only his lighted cigarette, or something like
that, and where would we be?"

"But there was the signal with the white cloth," added Joe.

"Yes, we could tell that, too; but it isn't positive."

"And there was Secor's running into me and spoiling our other films,"
said Charlie.

"That, too, would hardly be enough," went on Blake. "What the
authorities will have to do will be to search the baggage of these
fellows, and see if there is anything incriminating among their papers.
We can't do that, so we'll have to wait."

And wait they did. In spite of what Captain Merceau had said, the boys
did not relax their vigilance, but though, to their minds, the two men
acted suspiciously, there was nothing definite that could be fastened on
them.

Watchful guard was maintained night and day against an attack by
submarines, and though there were several alarms, they turned out to be
false. And in due season, the vessel arrived at "an English port," as
the papers stated.

"Let's go and see if Captain Merceau wants us to give any evidence
against those fellows," suggested Joe; and this seemed a good plan to
follow.

"Ah, yes, my American friends!" the commander murmured, as the boys were
shown into his cabin. "What can I do for you?"

"We thought we'd see if you wanted us in relation to the arrest of Secor
and Labenstein," answered Blake.

"Ah, yes! The two men who signaled the submarine. I have had them under
surveillance ever since you made your most startling disclosures. I sent
a wireless to the war authorities here to come and place them under
arrest as soon as the vessel docked. I have no doubt they are in custody
now. I'll send and see."

He dispatched a messenger who, when he returned, held a rapid
conversation with the captain in French. It was evident that something
unusual had taken place.

The captain grew more excited, and finally, turning to the boys, said in
English, which he spoke fluently:

"I regret to tell you there has been a mistake."

"A mistake!" cried Blake.

"Yes. Owing to some error, those men were released before the war
authorities could apprehend them. They have gone ashore!"

CHAPTER XIII

UNDER SUSPICION

Blake, Joe and Charles looked at one another. Then they glanced at
Captain Merceau. For one wild moment Blake had it in mind to suspect the