He climbed the hill, zigzagging back and forth to make easier work for the pony, until he was high above the live-oak belt and coming into shale rock and rubble that made hard going for the horse. He dismounted, led the pony to a shelving, rock-made shade, and tied him there. Then, with canteen and food slung over his shoulder, Johnny climbed to the peak and sat down puffing on the shady side of one of the twin columns. Seen close, they were huge, steeple-like outcroppings of rock, with soil-filled crevices that gave foothold for bushes. In all the country around Johnny could see no other hilltop that in the least resembled this, so it did not seem to him likely that he would ever miss his way when he travelled the air lanes. For awhile he sat gazing out over the country, which seemed a succession of green valleys, hidden from one another by high hills or wooded ridges. Mexico lay before him, across the valley and a hill or two--fifteen miles, Cliff Lowell had told him. It would be extremely simple to fly straight toward this particular hill, circle, and land down there in front of the oak. Cliff had spoken of risk, bat Johnny could not see much risk here. It must be across the line, he thought. Still, Cliff had said he had friends there, which did not sound like danger. They had considered it worth fifteen hundred a week, though, to fly across these fifteen miles into Mexico and back again. Johnny shook his head slowly, gave up the puzzle, and took out his wallet to count the money again. Half an hour he spent, fingering those bank notes, gloating over them, wondering what Mary V would say if she knew he had them, wishing he had another fifteen hundred, so he could pay old Sudden and be done with it. An unpleasant thought came to him and nagged at him, though he tried to push it from him; the thought that it would be Sudden's security that he would be risking--that the Thunder Bird was not really his until he had paid that note. The thought troubled him. He got up and moved restlessly along the base of the towering rock, when something whined past his ear and spatted against a bowlder beyond. Johnny did not think; he acted instinctively, dropping as though he had been shot and lying there until he had time to plan his next move. He had not been raised in gun smoke, but nevertheless he knew a bullet when he heard it, and he did not think himself conceited when he believed this particular bullet had been presented to him. Why?