he had the other end of this chain in his possession, then
it might be pretty definitely assumed that he was the man who was in the
battery room."

"The chain--perhaps," said the captain slowly, "although that seems
doubtful. As to the shirt, no."

And, unbuttoning his jacket, he produced from beneath it a torn and
crumpled brown woolen shirt.

"We found this about twenty feet from here as we were on our way," he
continued. "It resembles, but it is not, a regulation army shirt. It is
of the same texture and color, but it differs in minor details easily
discernible. It is my opinion that the man who wore this shirt bought it
and wore it for this very purpose, so that, if necessary, he might
discard it and still have the one which came to him through the
Quartermaster's Department. We evidently have to deal with a very crafty
enemy, and one as bold as he is unscrupulous.

"Lieutenant, what do you make of his manipulations in the battery room?"

"There is no doubt in my mind, sir," Lieutenant Mackinson answered,
"that he was about to connect up this instrument and then hide it for
future use where it could not easily be seen."

"I believe you are right," said the captain. "And then what use did he
intend to make of it?"

"Evidently his intention was not a loyal or friendly one," the junior
officer continued. "It would seem to me that his probable purpose was to
divulge to German submarines our whereabouts when we came within their
zone."

Apparently the commander of the ship agreed with him, for he made no
immediate answer. For several moments he remained in meditative silence,
his brow wrinkled, as though he was turning the whole thing over and
over in his mind.

"From the very fact that he wore such a garment," the captain said at
last, "it would seem that this man is among the regularly enlisted men
on this ship. However, that is by no means certain. There is this
certainty, however: If he would go to such desperate lengths once, there
is every possibility that he will do so again--only more cautiously than
before, for now he knows that his presence on board is known.

"The most rigid investigation must be started at once, and for that,
Lieutenant, I will require your assistance. Leave these young men in
charge of the wireless room, unless something unusual or in the nature
of an emergency occurs.

"As for you gentlemen," he continued, turning toward the three boys from
Brighton, "you are commanded not to