"I suppose those English swine are sound asleep," said a voice which the sub recognized as that of Kapitan von Riesser. "I cannot hear them grunting--we did last night." "Nor can I, sir," replied Unter-leutnant Klick, who as officer of the watch was accompanying the captain on his rounds. "But they must be. They went for that doctored sherry like fishes." "Himmel! That is good news," exclaimed von Riesser. "It will be quite safe to settle that vessel. When she first answered our call she was only forty kilometres away. In twenty minutes----" The listener fancied he could hear the kapitan rubbing his hands with glee. "It is much the better way," continued von Riesser: "'Lost with all hands' is quite a plausible theory. I am almost sorry we didn't wait until night when we tackled the Japanese ship. We run a good risk of being made a quarry for a dozen or more of those accursed cruisers. Those English may even send some swift destroyers on our track. You are sure those fellows are quite insensible?" "As quiet as the grave, sir," assured the unter-leutnant. "They will hear nothing. Even that terrific explosion when our torpedo took the Frenchman by surprise never disturbed them. But, of course, sir, I'll make doubly sure. We'll squirt some chloroform into the cabin." "Then be sharp about it," said von Riesser. "There's no time to be lost. That English vessel ought to be in sight within the next quarter of an hour." The German officer moved away. In a trice Denbigh communicated the news to his companions. "Oh for a respirator!" whispered O'Hara. "Don't worry," said Stirling. "The electric fan will carry off the fumes as quickly as they pump them in." Even as he spoke the fan ceased to revolve. The current actuating the ventilating gear had been switched off. Already Unter-leutnant Klick was putting his scheme into effect. "Those voice tubes," hissed Denbigh. "They lead nowhere," protested Stirling. "They are blocked. I tried them some time ago." The cabin had previously been used as the purser's office, and from it voice-tubes had communicated with the captain's cabin, the head steward's quarters, and the clerk's office. The metal pipes had been removed, but three lengths of flexible tubing had been left. With a sharp tug Denbigh wrenched one of the tubes from the flange securing it to the bulkhead. The second gave more trouble. As he was straining at it a sharp rasping sound fell upon his ear. In the adjoining cabin someone was at work drilling a hole through the metal partition. Smearing the bell-shaped mouth-pieces of two of the detached pipes with soap from the wash-basin, Denbigh clapped them together. "Hold on here, Pat," he whispered. "Press 'em tightly." O'Hara obeyed unhesitatingly. Instinctively he realized that this was Denbigh's pigeon, and once Denbigh undertook a task he was pretty certain of the result.