The Plesiosaurus made no attempt to reach out for him apparently, or, if it did, Dick knew nothing about it, but he swam on, possessed of the horrible fear of feeling those great teeth dug into his legs. Nothing of the sort happened, but something else did, almost as serious. Before he knew it Dick found himself suddenly caught in some undercurrent which seemed to draw him along with frightful rapidity down deeper and deeper into the lake. Dick was a splendid swimmer--it would have been difficult to find a better one in a boy of his age. He tried to turn aside out of the current to rise to the surface--to do anything to escape that awful suction, but it was all no use. Naturally he gave himself up for lost and he surely would have been if relief had not come in a moment, for all at once Dick’s head came up out of the water, although he had sunk to a great depth. But the suction continued and the current ran just as swiftly. It was pitch dark. Dick could not make out where he was, but the rushing of the water seemed to be echoed back from rocks, which were close at hand, so he assumed that he must be in some cave. On he flew--on--on for fully ten minutes. He had thrown himself on his back now and was resting comfortably enough, but, try all he would, he could not turn out of that terrible current, for he was in the subterranean outlet of the lake, one of those underground streams often found in the far West. Dick had read enough about them to realize the situation, and as he knew perfectly well that many of these underground streams never come to the surface, the prospect was anything but encouraging. All at once the strength of the current seemed to slacken--a little further on it grew less still until at last there was scarcely any movement at all and just then, to his great joy, Dick caught sight of a patch of moonlight striking across the water on ahead, which showed him the black, dripping walls of the cave. “There’s an opening there,” he thought. “I’m saved if I can only get through it. I must. If it isn’t big enough to let me through I shall give up in despair.” His heart almost stood still as he thought of this new danger, but he swam on and in a moment was crawling through a narrow opening, which brought him out upon a ledge of rock under some towering cliffs, where he sank down too much exhausted to hold his head up, and lay so for several moments, when all at once he was aroused by hearing a voice below him say: “They are coming! I can see them. It’s just Bill and the girl.” “Ah, but I can’t see nothing--hold on! I’m lying. I do see them. Yes, it’s just Bill and the girl, as sure as fate, Mr. Mudd.” The pronouncing of the name put Dick on the alert instantly. The two men, whoever they might be, seemed to be just below the ledge upon which he was resting. He crawled to the edge and looked down. Now, for the first time, he perceived his true situation.