For a moment, at sight of the deserted cabin, staring at Tom and his friend, as it were, from its hiding place amid the trees, the young inventor and his companion did not move. They just stood looking at the place.

"Well," said Tom,. at length, "we found it, didn't we

"We found something anyhow," agreed Jackson. "Whether it amounts to anything or not, we've got to see."

"Come on!" cried Tom, impulsively. "I'm going to see what's there."

"There doesn't appear to be much of anything," said Jackson, as he looked toward the lonely cabin with critical eyes. "I should say that place hadn't been used, even as a chicken coop, in a long while."

"We can soon tell!" exclaimed Tom, striding forward.

"Wait just a minute!" cried his companion, catching him by the coat. "Don't be in such a hurry."

"Why not?" asked Tom. "There isn't any danger, is there?"

"I don't know about that. There's no telling who may be hidden in that cabin, in spite of its deserted appearance. And though there aren't any 'No Trespass' signs up, it may be that we wouldn't be welcome. If there are some tramps there, which is possible, they might take a notion to shoot at us first and ask questions as to our peaceable intentions afterward--when it would be too late."

"Nonsense!" exclaimed Tom. "There aren't any tramps there and, if there were, they wouldn't dare shoot. I'm going to see what the mystery is--if there is one."

But there was no sign of life, and, taking this as an indication that their advance would not be disputed, Jackson followed Tom. The latter advanced until he could take in all the details of the shack. It was made of logs, and once had been chinked with mud or clay. Some of this had fallen out, leaving spaces between the tree trunks.

"It wasn't a bad little shack at one time," decided Tom. "Maybe it was a place where some one camped out during the summer. But it hasn't been used of late. I never knew there was such a place around here, and I thought I knew this locality pretty well."

"I never heard of it, either," said Jackson. "Let's give a shout and see if there's any one around. They may be asleep. Hello, there !" he called in sufficiently vigorous tones to have awakened an ordinary sleeper.

Put there was no answer, and as the shadows of the night began to fall, the place took on a most lonely aspect.

"Let's go up and knock--or go in if the door's open," suggested Tom. "We can't lose any more time, if we're to get out of here before night."

"Go ahead," said Jackson, and together they went to the cabin door.

"Locked!" exclaimed Tom, as he saw a padlock attached to a chain. It appeared to be fastened through two staples, driven one into the door and the other into the jamb, at right angles to one another and overlapping.

"Knock!" suggested Jackson. But when Tom had done so, and there was no answer, the machinist took hold of the lock. To his own surprise and that of Tom, one of the staples pulled out and the door swung open. The place had evidently been forced before, and the lock had not been opened by a key. The staple had been pulled out and replaced loosely in the holes.

For a moment nothing could be made out in the dark interior of the shack. But as their eyes became used to the gloom, Tom and his companion were able to see that the shack consisted of two rooms.

In the first one there was a rusty stove, a table, and some chairs, and it was evident, from pans and skillets hanging on the wall, as well as from a small cupboard built on one side, that this was the kitchen and living room combined.

"Anybody here?" cried Tom, as he stepped inside.

Only a dull echo answered.

The two could now see where a door gave entrance to an inner room, and this, a quick glance showed, was the sleeping apartment, two bunks being built on the side walls.

"Well, somebody had it pretty comfortable here," decided Tom, as he looked around. "They've been cooking and sleeping here, and not so very long ago, either. It wouldn't be such a bad place if it was cleaned out."

"That's right," agreed Jackson. "Wouldn't mind camping here myself, if there was any fishing near."

"The river can't be far away," suggested Tom. "And now let's see what we can find, and see if we can get a line on who has been here. But first we'll let in a little light."

He opened a window in the sleeping room, and pushed back the heavy plank shutter that had been closed. When the light entered it was seen that both bunks bore evidence of having been lately slept in. The blankets were tossed back, as if the occupants had risen, and in the outer room, on the stove, were signs that indicated a meal had been served not many days gone by.

"Now," observed Tom musingly, as he wandered about the place, "if we could only find out who owns this, and who has been here lately--"

Jackson stooped over, and, thrusting aside an end of the blankets that trailed on the floor from one of the bunks, picked up something.

"What is it?" asked Tom.

"Looks like a leather pocketbook," was the answer. "That's what it is," the mechanic went on, as he held the object to the light. "It's a wallet."

"Let me see it!" exclaimed Tom quickly. He took the wallet from the hands of Jackson. Then the young inventor uttered a cry. "A clew at last!" he exclaimed. "A clew at last! Mr. Nestor has been in this cabin!"

"How do you know?" asked Jackson quickly.

"This is his wallet," said Tom excitedly. "I've often seen him have it. In fact he had it with him on Earthquake Island, the time I sent the wireless message for help. I saw it several times then. He kept in it what few papers he had saved from the wreck. And I've seen it often enough since. That's Mr. Nestor's wallet all right. Besides, if you want any other evidence--look!" He opened the leather flaps and showed Jackson on one, stamped in gold letters, the name of Mary's father.

"Well, what do you make of it, Tom?" asked the mechanician, as he finished his examination of the wallet. "What does it mean? The pocket-book is empty and that--"

"Might mean almost anything," completed Tom. "But it's a clew all right! He's been here, and I'm pretty certain he was brought here in the auto with the odd tires--the one Mr. Damon and I saw traces of the night we heard the cries for help."

"But that doesn't help us now," said Jackson. "The point is to find out how lately Mr. Nestor was here, and what has happened to him since. There isn't anything in the wallet, is there?"

"Nothing," answered Tom, making a careful examination so as to be sure. "It's as empty as a last year's bird nest. He's been robbed--that's what has happened to Mr. Nestor. He was waylaid that night, instead of being run down as I thought--waylaid and robbed and then his body was brought here."

"There you go again, Tom! Jumping to conclusions!" said Jackson, with a friendly smile, and with the familiarity of an old and valued helper. "Maybe he's in perfectly good health. Just because you found his empty wallet doesn't argue that your friend is in serious trouble. He may have dropped this on the road and some one picked it up. I'll admit they may have taken whatever was in it, but that doesn't prove anything. The thing for us to do is to find out who knows about this shack; who owns it, on whose land it is, and whether any one has been seen here lately."

"They've been here lately whether they've been seen or not," said Tom positively. "There are the auto tracks. It rained two days ago, and the tracks were made since. Mr. Nestor must have been here within two days."

"He may or may not," said Jackson. "Say, rather, that some one was here and left his wallet after him. Now see if we can find other clews!"

They looked about in the fast fading light, but at first could discover nothing more than evidences that three or four persons had been living in the shack and at some recent date--probably within a day or two.

They had had their meals there and had slept there. But this seemed to be all that could be established, other than that Mr. Nestor's wallet was there, stripped of its contents.

Tom was looking through the closet, from which a frightened chipmunk sprang as he opened the door. There were the remains of some food, which accounted for the presence of the little striped animal. And, as Tom poked about, his hand came in contact with something wrapped in paper on an upper shelf. It was something that clinked metallicly.

"What's that?" asked Jackson. "Knives, or some other weapons?"

"Neither," answered Tom. "It's a couple of files, and they've been used lately. I can see something in the grooves yet and--"

Suddenly Tom ceased speaking and drew from his pocket a small but powerful magnifying glass. Through this he looked at one of the files, taking it out in front of the shack where the light was better.

"I thought so!" he cried. "Look here, Jackson!"

"What is it?"

"Another clew!" answered Tom.