This was evident, but it was also evident that Del Pinzo and his conspirators were sufficiently in advance to escape. For, with another sudden turn, the passage led to another natural, rocky stairway, and when this had been mounted the boy ranchers found themselves again in the main tunnel. "What's this?" cried Bud, when it was evident that they had come back to the place whence they had started, but farther on, and nearer to the river end of the tunnel. "This is a regular maze!" "But where is Del Pinzo?" asked Dick. "Out there, I fancy," and Nort pointed to where the main tunnel extended under the mountain and beyond, to the dam in Pocut River. "They've gotten away!" "And about time, too!" added Snake, "or they'd be trapped as we may be!" "Trapped!" cried Old Billee. "What do you mean?" "I mean there's a mine set here, somewhere! Don't you smell powder smoke?" A sharp, acrid odor, once smelled never forgotten, came to the nostrils of all as they stood there in the tunnel, while the stream flowed beside them. Whatever the conspirators had done, they had, evidently, not shut off all the water. "There it is!" cried Dick, and he pointed to where, in the light of the lanterns, there could be seen, slowly ascending, a thin wisp of smoke. "Look out!" yelled Old Billee as Dick dashed forward. "It may explode!" Then, as Dick rushed up with his lantern, they saw trailing over the floor of the tunnel, and on the same side of the stream as themselves, a thin white fuse, like a sinister snake. It was this burning fuse which caused the smoke. It was the work of but an instant for Dick to step on it, and extinguish the smouldering spark, while it yet had some distance to travel before the fuse lost itself in a mass of rocks. "Whew! That was a close call!" exclaimed. Bud, when the fuse was entirely out. "Let's see where it leads to," suggested Snake. They followed it up, and discovered a hidden mine of explosives, tamped down into a hole that had been drilled in the rocky floor. Iron bars, hammers and other mining implements showed that the perpetrators of the dastardly deed had evidently fled in a hurry. "They were going to blow up the tunnel!" cried Nort. "And when that collapsed it would mean the end of Flume Valley," spoke Bud soberly. "We never could have opened the tunnel again, with all these strange, branching streams playing around inside." "But we reached here just in time!" declared Old Billee. "Now let's get t' th' bottom of this. We know there's a main stream, an' two branching streams. One of th' branching streams is controlled by th' water gate with th' copper handle."