“He’s around here somewhere,” said Dick. “There’s no mistaking that melodious voice, but where?”

Suddenly another strange sound broke upon the air; half scream, half roar, and then a tremendous splash was heard over in the direction of the next cove.

The boys and Doctor Dan, seizing their rifles, ran that way, but before they got to the bend of the rocks they were able to see what was going on.

It was such a combat as probably no man on earth ever witnessed before.

There was old P. D. and a monster precisely similar to the one the boys had seen on the other side of the lake hard at it, and a bellowing and roaring broke upon the air that was fairly deafening.

The Plesiosaurus would rear its ugly head far above the water and strike with lightning rapidity at its antagonist, which would dodge and then dart forward, squirting up two vast streams of water out of holes in each side of its huge snout, snapping its crocodile-like jaws and displaying its terrible teeth.

For about twenty seconds the boys were treated to this wonderful exhibition and then, with a fearful splash, monster No. 2 leaped half its length out of the water, caught old P. D. by the neck and dragged him down out of sight.

“By gracious!” cried Charley. “That’s great!”

“Tremendous!” echoed Dick. “Who on earth ever saw the like?”

“I’ll bet on old P. D. every time,” chuckled Doctor Dan, relaxing his gravity for once and indulging in a hearty laugh. “It don’t seem to strike you as comical as it does me, boys. It’s one of the funniest things I ever saw.”

Dick failed to see where the laugh came in, but he said nothing and for some time they stood watching for the reappearance of the monsters, but the moments passed and they did not come to the surface again.

“There must be more than one Plesiosaurus,” remarked Dick, as they sat at supper; “by the way, Doctor, you were going to tell us of your discovery and how we could capture old P. D.”

“Why, there is a cove around on the western shore that has a very narrow entrance,” replied Doctor Dan. “There are great stones scattered all around there and there is one that I am sure would choke up the entrance if it was dropped between the ledges. Now if we could rig up some sort of a snare in the cove with the ropes we have brought and then pry the boulder over into the break and choke it up we would have our friend P. D. hard and fast.”

“Always providing he is obliging enough to go into the cove and run into our snare,” said Dick. “Well, we will take a look at it in the morning and see what we can make out of it. I’m dead tired now and I’m going to turn in.”

The tents had been moved further up the bank and as Doctor Dan had agreed to watch until morning Dick and Charley now wrapped themselves up in their blankets and put in a good night undisturbed.

Doctor Dan had no news to report in the morning and after breakfast he went up on the ledges, wrapped himself in his blankets and went to sleep there, telling the boys that they need not trouble their heads about him, but just do whatever they pleased.

“Let’s try the underground passage, Dick,” said Charley. “I’m wild to know if my theory is correct.”

“If I knew where we could dive and strike it I’d say yes in a minute,” replied Dick, “but I could never locate the place and I don’t care about running the horses around to the other trail without Doctor Dan.”

“I suppose that means we are to go across the lake again and see what we can find of the girl?”

“That’s what we ought to do.”

“Then by all means let’s do it. Duty first and pleasure afterward. How long do you intend to stop up here, anyhow?”

“Oh, a day or two. If we fail entirely I think I shall try to persuade Doctor Dan to take me on to Mr. Eglinton’s mine and see if Clara is safe there.”

“That means time lost. How about telegraphing Professor Poynter?”

“We can do that from the mine just as well as from Node Ranch. No doubt there is a line through to there.”

“The girl is a nuisance,” declared Charley. “I really believe you are ready to fall in love with her, Dick.”

“I’m ready to help her if she needs help and to save her from that scoundrel Mudd,” declared Dick, “but don’t let’s do any more talking until we have made a start.”

The boat was soon stretched and the seats placed and the boys then carried it down to the lake and got in.

It was not a pleasant craft to navigate, but Charley had become quite skillful with the paddle and they were soon making good headway across the lake.

“If we happen to run into old P. D. or his enemy there’s going to be an interesting time of it,” observed Dick. “You don’t say a word about that, Charley, but I know you are thinking about it all the same.”

“And why not?” replied Charley. “Of course I’m thinking about it, but what’s the use talking? We have just got to take our chances. When I’m out on an expedition like this I don’t believe in showing the white feather. It isn’t my style nor yours, either, Dick.”

“If it was mine you bet I wouldn’t be here,” said Dick, “but the danger is real just the same.”

Charley paddled on until at last they reached the other side of the lake and pulled up their boat on the shore close to the hut.

It still wore the same air of desertion. Dick had left the door partly open and had placed a small pebble on top of it in such a manner that if the door was touched the stone would be sure to fall.

He seized hold of the door and pulled it open, but no pebble fell.

“There’s been some one here!” he exclaimed. “Look, Charley, the floor is all tracked over with alkali since we were here.”

“That’s what, Dick. If it was mud, now, we might guess it was your friend.”

“Ten to one it was Mudd,” replied Dick. “Hello, what’s this?”

In the middle of the long table which occupied the centre of the room lay a paper upon which some words were written, fastened to the table by a rusty old bowie knife which had been driven deep into the wood.

“That’s yours, Dick,” cried Charley. “Don’t you see what it says?”

“For you, Dick Darrell,” were the words scrawled over the paper in letters at least six inches long.