Although there were plenty of opportunities, Kapitan Schwalbe made no attempt to molest the ships. For one thing, experience had taught him that the British merchant skipper possessed a bull-dog tenacity, and a courage not to be daunted by the sight of a hostile periscope appearing from nowhere in the midst of a waste of water. For another, he was now on the look-out for more important game—his chance to retrieve his already vanishing prestige.
However, one of the merchant vessels served him a good purpose, although unknown to her. Marking a large ocean tramp bound up-Channel, U75 dived deeply, so as to be free from any danger of being hit by her forefoot.
With the noise of the tramp's propeller to guide her, U75 followed, unsuspected, in her wake as she made for the Lizard Light.
Arriving safely at the rendezvous, Kapitan Schwalbe waited until it was dark, and then cautiously brought the submarine awash. Punctually at ten o'clock a feeble violet light blinked through the night. It was U77's call to her consort.
"What's the game, I wonder?" asked Vernon, as a hail in German was borne faintly to their ears.
The chums had turned in. There was nothing else for them to do, since they had been ordered to leave the quarters allotted to the crew. As there was no furniture of any description in the alley-way that had been made their sleeping compartment, they had climbed into their bunks. Here they could maintain an almost uninterrupted conversation.
"Hist!" exclaimed Ross warningly. He had been lying with his ear almost touching one of the many voice-tubes that led from the conning-tower to various parts of the submarine. Quite by accident, he discovered that the pipes formed an excellent conductor of sound in a manner that had not been intended.
"What are you doing?" asked Haye curiously.
"Jam your ear against the centre one of these three pipes," said his chum.
Vernon did so. It required very little movement on his part, since the bunks were rather narrow. The same voice-tube that Ross was "tapping" ran vertically past Haye's bunk, which was immediately underneath the one Trefusis had appropriated from the time when he had been laid upon it under the influence of the injection.