ld be a reason for the train
robbers hanging to father, if they found him, wouldn't it?"

"I don't understand," replied Will.

"Why, if father knows a lot of passages and hiding places and empty
river channels, in this section, he's just the man the train robbers
would want to tie to."

"I understand now," Will replied. "And you remember, too," he continued,
"how mysteriously the three men disappeared last night? Why, they got
out of sight as quickly as if they had been painted on a slate and
rubbed out."

"That's a fact!" replied Chester.

"There's one thing about it," Will argued, "the train robbers won't dare
to go on into the bad lands, for they have no supplies, and their horses
must be about used up. By remaining here, they may be able to steal
supplies and, possibly get out to Lander and buy some."

"I guess we've got it doped out all right," Chester answered. "All we've
got to do now is to go on and see whether we have or not."

The boys pressed on to the back of the first cavern and turned to the
right into one which ran parallel with it. Their lights showed that a
fire had been built in the tunnel connecting the two. There were also
empty tin cans and cardboard food packages scattered about.

"This looks like population," grinned Will.

"Isn't this the spot from which the men disappeared?" asked Chester.

"Unless I am much mistaken," Will returned, "the three men were in front
of a fire in this tunnel. Say, but they did get out of sight quick,
didn't they? It was like the scene from the Black Crook."

"Then the passage they crawled into can't be far away," Chester
volunteered, "at any rate, right here's where we want to make our
search!"

"There's no knowing where this wrinkle leads to," Will said as the
lights pierced the narrow channel. "If we get down there, we may never
be able to get back."

"Father must have known of this place," Chester said, "and that's why he
talked about moving our camp here."

"Well, if he used the passage, we certainly can!" replied Will.

"Are we going down now?" asked Chester.

"I'm game for it."

"Well, then, wait a minute!"

Chester ran to the entrance of the cavern and looked up and down the
gorge and valley. When he returned there was a worried look on his face.
He pointed to the dry channel and said:

"We may as well be getting down there. There's some one coming."

"Who is it?" asked Will.

"I couldn't distinguish faces," was the reply.

"Wasn't