Jan was as good as his word. That night the fugitives slept comfortably in the cabin of the mate of the steamship _Hoorn_; and at tide-time, early on Saturday morning while it was still dark, the vessel glided between the breakwater of Ymuiden, and shaped a course for the mouth of the Thames.
"What's that light, Jan?" asked the Flight-Sub.
The _Hoorn_ was now well beyond the three-mile limit. Ross and his fellow-passenger were standing aft, sheltering from the keen south-westerly wind. The mate of the vessel was with them, the skipper being on the bridge.
"Those lights?" corrected Jan. "They have been visible all the time. They are the two white leading-lights to Ymuiden harbour."
"No, I don't mean those," said the Flight-Sub. "Away to the south'ard, quite a mile from the harbour. See, it's showing again."
From the dunes a white light blinked thrice and then disappeared.
"I do not know," answered Jan gravely. He thought for a moment and then said: "Half a mo'. I will speak to the skipper."
"Hanged if I like it," muttered the Flight-Sub. "I say, Trefusis, that light blinking away looks very fishy. It would mean a fifty-pound fine in England; but here, apparently, it is not objected to."
The skipper and the mate were talking rapidly. Both men were leaning over the after side of the bridge-rails, with their eyes fixed upon the dark shore from which the mysterious light flickered at regular intervals.
"Light on the port bow," reported the helmsman. Both of the _Hoorn's_ officers turned just in time to catch sight of a steady white light before it disappeared. Whatever its meaning, it was remarkable that from that moment the shore light ceased to blink.
"Put out our navigation lamps, Jan," said the skipper. "Someone has betrayed your English friends. Nevertheless I will do all in my power to aid them. We'll steer south-west for an hour. Perhaps we may outwit yon craft, whatever she may be, before dawn."
Ross and his companion were quick to note the alteration of helm. They knew, too, that the removal of the steaming-lights was for the purpose of baffling what must be, to a dead certainty, a German craft--a submarine, or perhaps a torpedo-boat, since the latter frequently ventured out of Borkum and crept stealthily towards the Schelde, keeping close to the Dutch territorial waters in order to avoid being snapped by the vigilant British destroyer flotilla.