The young officer stepped into the battery room, returning with a small, but evidently powerful, portable wireless transmitter and receiver. "H'm," exclaimed the captain, examining it carefully. "Of German make." "Exactly, sir," replied Lieutenant Mackinson, "and evidently quite new--probably never used more than once or twice before." "This is very serious business," said the captain impressively. And then, addressing Joe: "Did you get a look at the other man? Would you know him if you ever saw him again?" "No, sir, I did not even get a glimpse of him. But I thought, sir, that perhaps----" "Yes," encouraged the captain in a kindly tone. "Go on with your suggestion." "I thought, sir," Joe continued, "that if we could find a man aboard with his shirt torn in such a way that this piece would fit, and especially if 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.