As the express trains were almost invariably stopped at night, the expert travelled at night and slept by day. Months passed with only two or three "signals." These happened to be on the train opposed to the one in which the detective was travelling at that moment. They brought out another man, and on his first trip, taken merely to "learn the road," the train was stopped in broad daylight. This time the stop proved to be a lucky one; for, as the engineer let off the air and slipped round a curve in a canon, he found a rock as big as a box car resting on the track. The detective was unable to say who sounded the signal. The train crew were overawed. They would not even discuss the matter. With a watchman, unknown to the trainmen, on every train, the officials hoped now to solve the mystery in a very short time. The old engineer, McNally, who had found the rock in the canon, had boasted in the lodge-room, in the round-house and out, that if ever he got the "ghost-sign," he'd let her go. Of course he was off his guard this time. He had not expected the "spook-stop" in open day. And right glad he was, too, that he stopped _that_ day. A fortnight later McNally, on the night run, was going down Crooked Creek Canon watching the fireworks in the heavens. A black cloud hung on a high peak, and where its sable skirts trailed along the range the lightning leaped and flashed in sheets and chains. Above the roar of wheels he could hear the splash, and once in a while he could feel the spray, of new-made cataracts as the water rushed down the mountain side, choking the culverts. At Crag View there was, at that time, a high wooden trestle stilted up on spliced spruce piles with the bark on. It used to creak and crack under the engine when it was new. McNally was nearing it now. It lay, however, just below a deep rock cut that had been made in a mountain crag and beyond a sharp curve. McNally leaned from his cab window, and when the lightning flashed, saw that the cut was clear of rock and released the brakes slightly to allow the long train to slip through the reverse curve at the bridge. Curves cramp a train, and a smooth runner likes to feel them glide smoothly. As the black locomotive poked her nose through the cut, the engineer leaned out again; but the after-effect of the flash of lightning left the world in inky blackness. Back in a darkened corner of the drawing-room of the rearmost sleeper the sleuth snored with both eyes and ears open.