From the fields in which they had descended to the inn the distance, as nearly as he had been able to guess it, was about a mile. He shortened this somewhat on the return trip. And he was within a quarter of a mile of the meeting place when he became suddenly conscious of something that was not just right. At first he was tempted to stop, but he overcame the temptation. The thing that had warned him of a possible danger was a trifling noise, yet one that was out of the ordinary. What the noise was he could scarcely have told. Perhaps the breaking of a twig, perhaps the slipping of a foot along a suddenly encountered patch of mud. At any rate he was sure that he had been followed. 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.