A minute later and they both caught the far-away sound of what seemed to be the winding blast of an Alpine hunter’s horn.
“Yes, it’s Pudge, all right, and he wants to hear from us if we’re within reach of the sound of his signal. Answer him, Billy!”
Already Billy had taken the horn from its fastenings, and no sooner had Frank given the order than he applied it to his lips. The sound that went forth, coming as it did from the blackness of the sea beyond, must have astonished any sailor on board the various steamers in the harbor.
Once, twice, three times did Billy give the peculiar note that Pudge knew so well. It must tell the absent chum that they were safe, and in the language of their secret code ask how things were going with him.
“There, he’s given us back the message word for word!” cried Billy, as they caught the faint but positive reply from the unseen shore, perhaps at the deserted hangar. “Frank, he’s all right! That takes a big load off our minds.”
“Yes, now I can rest easy!” declared the other. “As that star isn’t close to the sea as yet, Billy, if you don’t mind, I think I’ll try for a few more winks of sleep. Pudge will go back to town and stay at our lodgings until we turn up, or send him a message. Everything is working finely.”
“For us,” added Billy, chuckling. “But think how mad those spies must be over losing the prize they thought was sure to fall into their hands. Why, I wouldn’t be surprised if they discounted the capture of our seaplane, and over in Belgium were ready to start to work making copies of the same as soon as the sample could be delivered.”
Billy appeared to be highly amused, for he chuckled to himself for several minutes while picturing the disappointment of the baffled plotters. Then once more he settled down to his task of serving as “officer of the watch.”
As the minutes crept on, Billy began to observe the gradual approach of the star to the vague region where sea and heavens merged in one. In fact, Billy was yawning quite frequently now. He found himself fairly comfortable, thanks to the warmth of that leather fleece-lined jacket, and the hood which he had drawn partly over his head. Still, it was not very delightful, sitting there on the water; and perhaps the boy’s thoughts frequently turned toward the bed he was missing.
“I wonder which way we’re drifting now?” he suddenly asked himself; he immediately set to work trying to answer his question by observing the direction of the tide, as well as by the light current of air.