Dave came in sight and joined in the chase.

"What was it?" panted Dave, as he came within hailing distance.

"Someone running away from me," Dick explained.

"What did he look like?"

"I didn't have a chance to see. Let's travel hot-foot."

Yet presently Dick halted. Dave stopped beside him.

"We've passed him; he has doubled on us," uttered Darrin in a
tone of intense chagrin. "We belong in the primary class in wood
lore."

Then, suddenly, they heard a slight noise again. Forward they
dashed. Now they came out to a place where the ground was more
open. Before the two high school boys rose a great boulder of
rock, its front sloping backward, and running up to a height of
fifty feet or more. They had already seen this boulder from the
water.

"That fellow ran into the open, but he didn't have time to cross
it," announced Dick in a tone of conviction, as the pair halted
at the foot of the boulder. "He could have gone up this side;
there are crevices enough for foothold. But in that case we'd
have seen him."

Dave stood plucking absent-mindedly at the leaves of a bush in
a clump that grew at the foot of the boulder. Suddenly Dick glanced
down, noting that his feet were on boggy ground, though the surrounding
soil was firm enough.

"Is there a spring running out of the solid rock?" wondered Dick,
reaching out and pulling one of the bushes forward.

Then he gave a sudden shout of discovery:

"Look here, Dave! We're on the track of it! These bushes conceal
the mouth of a cave! This is where our fugitive has gone!"

CHAPTER XIII

PERHAPS TEN THOUSAND YEARS OLD

"By Jove!" gasped Dave, also bending back a bush and glaring down,
his eyes wide open with interest.

"That's where our man went," Dick whispered.

"Not a doubt of it," Dave assented. "We'll signal the other fellows,
and then get him at our leisure."

"Unless there are other openings to this cave," Dick hinted.

"That's so! The fellow may be a quarter of a mile away from here
already," Darrin quivered. "Let's not lose any time. I'll go
in there first."

Dave was on his knees, quivering with eagerness, dominated by
purpose, when Dick grabbed him, hauling him back.

"Let me alone," growled Dave. "Don't interfere with me!"

"But you don't know what you might run into in there, Darry,"
Prescott insisted firmly. "For one thing, you have no idea how
many villains may have their secret home in there."

"Then, what a