He slowed down and now he could hear, or thought he could, the heavy breathing of at least two men. He was not certain of this; he was willing to admit to himself that he might be fancying it.
"If they're after me, why don't they take me?" he wondered to himself. But the explanation came to him almost as soon as he had asked himself the question. Whoever was following him could reason from the sight of the can of petrol he was carrying that he was going to some definite place where that petrol was wanted. And it would require no great stretch of the imagination for his trailers to decide that he must be carrying fuel to the aeroplane that had worked such havoc with the German plans.
"They think I'll lead them to the 'plane," he thought. Half a dozen plans for misleading them came to him. But none seemed practicable. Frank was intensely dogged in his determination to accomplish anything he had set out to do. The idea of giving up now, even to mislead his pursuers and so save Captain Greene from capture, was repugnant to him. He wanted to foil the men behind him—unless, as was possible, he only imagined that they were behind him—and still do what he had set out to do, which was in this instance to refill that empty petrol tank on the monoplane.
It was the purely accidental movement of putting his hand into his pocket to dry it off that gave him the idea. It met the pocket flashlight Captain Greene had given him, and at once he remembered a use for it of which the aviator had told him. To follow the plan did not mean that it would succeed, but it represented a chance, anyhow. And so when he came to the fence which he remembered climbing on his way from the monoplane, he stopped on the top rail, having pushed his can of petrol through first. In the field now immediately in front of him, but far away still, on the other side of the field, lay the monoplane. He could not see it in the driving rain but he knew that it was there.
There too would be Greene, waiting for him, and in all probability at this moment straining his eyes watching for his return. On that depended his chance of success in the plan that had come to him. On that, and on Greene's presence of mind and quick-wittedness.
So, still astride of the top rail, he began signalling with his pocket flashlight. He spelled out his message in Morse code, using a long pressure of the releasing switch for the dash and a short one for the dot. Word by word he spelled out his message, telling that he suspected that at least two Germans were trailing him. And at the end he signalled a request that if he had understood, Greene should wait a half minute and then imitate an owl's cry. He chose an owl because he had heard one or two earlier in the night. And he added that if he got the signal he would keep on heading for the monoplane. He suggested nothing to Greene; the rest was decidedly up to the aviator. Frank had done his share.
If there were Germans actually within sight of him, they did not attempt to interfere with him while he was flashing his message. But he had reckoned confidently that they would not. He was sure that he had not betrayed the fact that he knew he was being followed, and they would naturally suppose that this stop for signalling was part of a pre-arranged plan. He now dropped to the ground, picked up his can and took two or three quick steps. Then he stopped abruptly and was sure that he heard a footstep behind him. He grinned to himself, and just then the hoot of an owl sounded. Then he went on.
"I'll make it easier for them," he said. "Perhaps they wouldn't like to follow me right across the field!"
So he skirted the fence and the hedge at the side, and went around three sides of the field to reach the monoplane. And, as soon as it was in sight, all his suspicions were verified, for from behind there came a sharp exclamation in German, and he was told to stop, just as a heavy hand gripped his shoulder.
"Ja, we were right!" exclaimed one man in German. "There is their aeroplane! Now for the other—"