As Rob toppled forward into vacancy, he received a startling momentary impression of familiarity from the tones of a loud laugh which rang out behind him. Fortunately for him, the water at the foot of the bridge abutment was some six or seven feet deep, and he struck it spread-eagle fashion, so that beyond the shock of his sudden fall he was uninjured. He at once struck out for the bank. When he stood again on the dry ground, shaking the water from himself, he began to rack his memory for the recollection of where and when he had heard a similar laugh to the one that had sounded in his ears as he plunged forward into space. Try as he would, however, he could not place it, and giving up the attempt finally, he made his way back to the hotel. The checker players started up as the dripping figure of the Boy Scout leader entered the room, and naturally began to ply him with questions. Rob's story of the events of the preceding few minutes was soon told, but so far as the shedding of any light on the mystery was concerned, it remained as blank a puzzle as ever. "I'd like to think that I dreamed it all," said Rob, "but these"--wringing out his wet clothes--"won't let me." "Well, there's no doubt that you were shoved over intentionally," decided Harry Harkness, "but who is there out here who would do such a thing?" "It might have been one of those two cow-punchers you had the row with this afternoon," suggested Merritt. "No. I saw Clark and Jess ride out of town a good half-hour before Rob could have been shoved over," said Harry. "Maybe they mistook me for some one else," suggested Rob, as the easiest way of disposing of the matter. Privately, though, he entertained a different opinion. If he could only place that laugh! But try as he would, he could not for the life of him recall where he had heard it before. Soon afterward the Boy Scouts and their ranch friend retired to bed, Tubby having been sufficiently aroused to make his way upstairs to their room. Tired out as Rob was, he sank into a deep sleep almost as soon as his head touched the pillow. With Tubby things were different, however. His nap in the chair had rendered him wakeful, and he tossed and turned till almost midnight before he began to grow drowsy. Just as he was dropping off, two persons entered the adjoining room. The partitions, as is usual in the West, were of the very thinnest wood, and he could easily hear every movement made by their neighbors. "Well, Jack," said one of the voices, evidently resuming a conversation that had been begun some time previously, "so you did the kid up, eh?" "Yes, sent him head first over the bank. Wish he'd broken his neck. The kid is one of that bunch that was responsible for my leaving Hampton." "Is that so? I don't wonder you are sore at him. Why didn't you hit him a good crack on the head while you were about it?"