you two formerly lived," said
Will. "For all we know, your father may be hiding there now."

"I know it," replied Chester, "but we came on so fast and in such a
state of excitement that we didn't think of doing so."

"Well, we mustn't let the others get too far ahead of us," Will
suggested. "They must be quite a ways off now!"

"Don't you think we can do a better job with them out of the way?" asked
Chester. "They go roaring along like a herd of elephants."

"I presume we can," replied Will. "Anyway we can make an investigation
of our own and then go back to camp. Sandy is alone there with his
wounded shoulder, and almost anything is likely to happen."

"We'll go into the cave I spoke about a moment ago," Chester said, "and
examine it thoroughly with the searchlights."

"What's the idea of that?" asked Will.

"Well, Tommy and George are in some one of these caves. They may be
hiding from us or they may have been captured by the train robbers. If
they are hidden away, they're quite likely to be in the large cavern I
spoke of. It won't do any harm to look through it."

"Why, that must be the cave where we saw the three men last night!" Will
exclaimed. "I have an idea that the three men we saw were the two train
robbers and your father."

"That was my idea at the time," the boy replied, "but now I can't quite
make up my mind that father would tie up with such a bunch."

"Bless your innocent soul," grinned Will. "Your father couldn't help
associating with them if they insisted upon it! I can see no reason why
they should want to molest him, but one can never account for the mental
processes of train robbers."

"I believe this is the same place!" Chester cried as they stepped
inside. "You know father often talked about moving to this cave, and
I've got an idea that he knows more about the locality than I do."

"In what way?" asked Will.

"Well, I think he found some secret passage here. I believe he knows how
to enter and leave this cavern without being seen. This whole ridge, you
know, is honeycombed with caverns and tunnels. I have been told," the
boy continued, "that the gorge and the valley to the east formed the
basin for a great lake, hundreds of years ago, and that the water seeped
through the limestone rock until there wasn't much left of it in some
places. There are certainly plenty of caves here!"

"I should say so!" replied Will turning on his searchlight.

"Look here," Chester went on, "that wou