The German eyed Dave Darrin curiously. The American officer's uniform was concealed under his sou'-wester, rubber coat and boots, but after a moment's inspection, the German said curtly: "You, too, will come aboard." As refusal would have been absurd under the circumstances Darrin promptly obeyed. Instantly the German officer snatched a fold of Darrin's rubber coat, pulling it aside and thus revealing a glimpse of the uniform beneath. "Take off that rubber coat!" the Hun ordered, brusquely. Flushing slightly, Dave obeyed, his uniform now being fully revealed. "Ha!" snarled the Hun. "I suspected something of the sort. You two will go down through the manhole. And this man and woman are passengers? They will come aboard." Captain Kennor led the way below, Mr. and Mrs. Launce following. Dave, as he reached the manhole, turned to see the "Rigsdak" vanish beneath the waters. Then Dave Darrin stepped inside the conning tower and began to descend the ladder--a German prisoner at last! CHAPTER IX THREATS TO A PRISONER AS for the seamen in the boat, the officer, after a scowling stare in their direction, ordered them also on board, where he had them lined up forward. "Take off those life-belts," he ordered, still in English, and a seaman who understood interpreted to his fellow-Danes. Off came the life-belts, which were dropped to the deck. German sailors then kicked them all overboard. Now the submarine began to move slowly. A shot was fired from the forward gun into the lifeboat, wrecking and sinking her. This done, the German seamen followed their officer in through the manhole, which was closed. For at least two miles the submarine moved along on the surface, then, slowly, began to submerge. One of the Danish sailors on deck set up a howl of fright when he found his shoes six inches under water. The cry was taken up by the other sailors with him. The water rose to their knees--higher. The conning tower settled down into the sea, and the wretched sailors of the captain's boat were left floundering in the water, without life-belts or anything buoyant to keep them afloat. The last vestige of the submarine vanished, leaving more than a dozen despairing men to flounder and to die, for the "Rigsdak's" other boats were now too far distant to see what had happened. Going below, Dave and his friends from the "Rigsdak" were conducted into a tiny wardroom behind the mess table at which sat a frowning, leering German ober-lieutenant. "A ship's master who did not like us well enough to bring his papers and his instruments," barked this commanding officer of the sea-hornet. "An Englishman and his young wife, eh? But we have here--?" "An American naval officer," replied the younger German officer. For some reason the ober-lieutenant's manner changed. He looked Dave over curiously, but without the same ferocity. "Be good enough to be seated," he said, with a wave of the hand toward a chair. "Let these swine stand!"