"Of course," Dave went on, "any other radio operator who is within hearing distance can pick up your messages, so you do not send them in open German but use a code, or rather, a series of codes." "If your radio men have ever picked up any of our messages," retorted the young German, "you must know that you were not able to decipher their meaning." "We could not always decipher them," Darrin admitted. "What do you mean by that?" "Why, it is possible, of course, that sometimes we and our Allies have some keys to the German use of code messages." "You assert that?" questioned von Schellen, rather eagerly. "No, and I do not deny it, either," Dave smiled. "You are interesting, but discreet," complained the German, banteringly. "And I may say as much of you," Dave continued. "Naturally, you know some things that you would not tell me, and I know a few things that I would not dream of telling you." "And, instead, you hint at things that are not so, and perhaps I do about the same thing," returned von Schellen. After that silence fell for some minutes. Dave walked back and forth, the junior officer watching him keenly. Overhead the crackling at the aerials continued, with occasional intervals of silence when the operator below was busy receiving messages. Again a petty officer approached von Schellen, saluting and reporting in an undertone. "It is time for you to go below," announced von Schellen, turning to Dave. "I appreciate very much this opportunity to take the fresh air," Dave said, politely, as he turned toward the conning tower. "Oh, I guess you're welcome," said the lieutenant, shortly, and with a meaning smile, "though sometimes there is such a thing as too much outdoor life." To Darrin's mild astonishment, as he stepped below, a folding table had been set up, and around this were seated the ober-lieutenant and two other officers, one of them an engineer. Von Schellen, at a nod from his chief, made the fourth at the table. Into this cabin were brought the English couple and the Danish master. Several sailors stood about. The occasion began to take on a formal look, which was heightened when the ober-lieutenant laid on the table a small sheaf of papers. "First of all, you, Herr Darrin," began the ober-lieutenant. "There can be no doubt that you are Darrin?" Dave thrust a hand in under his sheepskin, bringing to light a card-case. From it he withdrew a pasteboard which he laid on the table. "That is my card," he said. The ober-lieutenant studied it deliberately, then passed it to another officer as he continued: "And you do not deny that it was you who captured Ober-Lieutenant von Bechtold of the Imperial German Navy. You were the principal witness against him when he was tried in Britain for being a spy?" "I do not deny it, sir." "That is all. You may step back." As Darrin drew back he could not escape the feeling that two of the seamen near him regarded him as being their especial prisoner.