y 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

"Looks to me as if we were going to be stumped, Jack."

"I agree, Andy. It doesn't look as if there were any mink in this
neighborhood," answered the oldest Rover boy.

"Don't give up yet," pleaded Fred, who sat on a fallen tree, resting.

"It's barely noon yet," announced Andy, glancing at his watch. "We've
half a day before us."

The boys had spent the entire time since leaving their cabin in skating
along the shore of the island and making their way along the tiny,
frozen-up watercourse, where they had hoped to discover at least one
brook mink. But the only game to come into sight had been a squirrel,
and they had not shot at this, fearing to disturb the other game, were
it in that vicinity.

"Let's have lunch before we continue hunting," suggested Andy. "This is
as good a spot as any to rest in."

The others were willing,