Barney Stevenson came out to see them off.

"Going down to that brook where you saw the mink?" he questioned, referring to a tiny watercourse, now, of course, frozen up, located near the southern end of the island.

"Yes. And maybe we'll get away down to the other cabin," answered Jack.

"We thought we'd like to take a look around there."

"And if we don't come back to-night, you'll know that we're staying at that cabin," said Fred.

"Oh, we didn't calculate to stay out all night," put in Jack quickly.

"I know we didn't. But it's just possible it may get too late for us to come back, and that cabin would be comfortable enough, especially if we managed to drag in some pine boughs for beds."

"Well, don't shoot more than half a dozen minks--or half a dozen deer, either!" shouted Uncle Barney after them; and then they started off and were soon out of sight, skating along the eastern sh.o.r.e of Snowshoe Island.

Left to himself, Uncle Barney began to pace the floor of his cabin impatiently. Evidently the old lumberman was turning over something in his mind--something which bothered him a great deal.

"Of course they are safe!" he murmured to himself. "It couldn't be otherwise. The last time I looked, the tin box was just where I had left it. I don't see why I should get so nervous over it."

Presently he drew out his pipe, filled it, and sat down in front of the fire to smoke. As he did this, a slight noise outside the cabin attracted his attention.

"I wonder what that was?" he asked himself, and, arising, looked out of one of the cabin windows. Then he went to the door and gazed around. No one was in sight, and he closed the door again.

"Must have been the wind, or something like that," he murmured. "Or else I'm getting more nervous than I ever was before. Now that I've got used to those boys around, it seems dreadfully lonely when they are gone;"

and he heaved a deep sigh.

He remained in front of the fire for the best part of half an hour.

Then, as if struck by a sudden determination, he leaped up, knocked the ashes from his pipe, and began to put on his snowshoes. He donned his heavy coat and his cap, locked up his cabin, and strode off in the direction of the heavy woods in the center of the island.

Although Barney Stevenson was not aware of it, the noise he had heard while seated before the open fire had betokened something of importance. Entirely unknown to the old lumberman or to the Rover boys, Slugger Brown and Nappy Martell had arrived in the vicinity of the two cabins on the northern point of the island. Both of the youths were armed, but they approached the cabin occupied by the old lumberman with the greatest of secrecy.

"It looks like another wild-goose chase to me," growled Slugger Brown, when they were close to the place. "We've been here three times now, and the old man hasn't done a thing out of the ordinary."

"Well, we're sure of one thing, anyway," Nappy replied. "He hasn't got those deeds anywhere around that cabin--or at least no place where we could locate them."

The bully and his crony had, from a distance, watched the departure of the Rovers. As can be guessed from their conversation, they had visited the island several times before, each time taking care that none of the others should discover their presence. On their trips they had been strongly tempted to "rough-house" the cabin occupied by Jack and his cousins, but they had not dared to do this, fearing it might cause the Rovers to go on guard.

"And anyhow, we're not here for that purpose now," Slugger Brown had observed. "We want to get those land deeds for my dad and old Lemon."

The two youths had come close to the side of the cabin and peered in at one of the windows, and it was this noise that had attracted Barney Stevenson's attention. But they had managed to keep out of sight of the old lumberman by flinging themselves down behind some bushes. They watched the departure of Uncle Barney with interest, and at once resolved to follow him.

"Of course we haven't any snowshoes; so maybe we won't get very far,"

said Slugger, "but we will do the best we can."

Unconscious that his movements were being so closely observed, Uncle Barney plunged deep into the woods, taking a trail which was familiar to him. In some spots the snow lay deep, but in the majority of places the wind had swept the ground almost bare, so Slugger and Nappy had no great difficulty in following in the old man's footsteps.

"He doesn't seem to be going out after any game," observed Nappy presently. "I just saw a rabbit running ahead of him, and he never even raised his gun."

"I think I know where he's going," answered Slugger. "We'll soon find out if I'm right."

"You mean that cave your father once spoke about?"

"That's it, Nappy."

"What is there about that cave that makes it so important?" went on the other curiously.

"Never mind that now--you'll know some day--when my father gets possession of the island," answered Slugger rather importantly.

The best part of half a mile more was covered, and then Barney Stevenson left the trail and plunged in among a wilderness of trees and rocks. He had to take off his snowshoes, and he hung them up in a tree. Then he went ahead once more, presently reaching the foot of a little cliff.

Here there was an opening six or seven feet in diameter, and he disappeared into this.

"What do you know about that?" cried Nappy in a low voice. "Is that a cave?"

"That's just what it is!" answered Slugger triumphantly. "I only hope it's the cave my father wanted to locate."

"Why does he want to locate a cave on this island?" asked Nappy, more curious than ever.

"You'll know some day, Nap. Now come on--let's try to find out what the old man is going to do in that cave."

With caution, the bully and his crony made their way over the snow, and then slipped inside the entrance to the cave. Ahead of them they saw the flicker of a lantern which Uncle Barney had lit.

The cave was irregular in shape, running back a distance of a hundred feet or more. As the old man advanced he held his gun ready for use, thinking that possibly some wild animal had taken possession; but no animal of any sort appeared.

Coming to the back end of the cave, the old man set down the lantern on a rock. Then he got down on his knees and began to pull away at a large flat stone, close by. He worked rather feverishly, as if growing more nervous every instance.

"It must be here! They couldn't have gotten it away from me!" he muttered to himself.

As he worked, Slugger and Nappy approached until they were within plain sight of what he was doing. They did not make a sound, however, and Uncle Barney never suspected their presence.

When the flat stone had been set aside, there was revealed a small _cache_, lined with more stones. At the bottom of this _cache_ rested a fair-sized tin box, dark blue in color, and secured with a padlock.

"Ha! I knew it was safe!" cried the old man in a relieved tone of voice.

"I knew they couldn't find it!"

"Say! what do you suppose----" began Nappy, when Slugger clapped a hand over his mouth.

The low-spoken words echoed throughout the cavern, and, much startled, Uncle Barney dropped the tin box and sprang to his feet. As he did this Slugger Brown shoved his crony behind a projecting rock, and crouched low himself.

"Who is there?" cried the old lumberman, and caught up his gun. "Who is there, I say! Speak, or I'll fire!"

For reply, Slugger picked up a good-sized stone which was handy. Taking hasty aim, he hurled it at the old man. It struck Uncle Barney in the forehead, and slowly the old lumberman sank to the floor of the cave unconscious.

CHAPTER XXVIII

UNCLE BARNEY'S SECRET