was a chance the
rebels could be persuaded to exchange father for Von Arnheim and
Morales. Stone might know how important those two worthies are
considered by the rebels."

"Can't I listen in on this confab?" Frank asked, plaintively. "Or
must I continue to mount guard here? Besides, I want to go down and
look at our airplane, and pat it even if I can't get in and fly. I can
see it from here, and it looks tempting."

"You'll have to wait awhile to do that, I expect," said Jack with a
smile. "We must decide what to do next before we spend any time
playing."

At that moment, Tom Bodine yawned prodigiously and sat up on his
make-shift couch.

"At least I can have a voice in the conference," said Frank. "If Tom's
awake he can mount guard."

"All right, fine," said Jack. "We'll leave him out here with Morales
and Von Arnheim, as soon as he has had something to eat. Then the
three of us can take Stone into the other room and have a talk with
him."

So it was arranged.

CHAPTER XXI

GAINING AN ALLY

Before mounting guard, however, Tom thought of their horses, a detail
which the boys had forgotten in the quick march of events. He and Bob
descended the slope, brought the animals into the valley where there
was grass along the bed of a little stream trickling from a spring,
and a few trees that provided shade. The horses were hobbled to
prevent wandering too far, and then left to do as they pleased. They
pleased, every one, to lie down at once and roll.

Upon their return to the cave, after Bob first had inspected the
airplane and found it in tiptop condition and stocked with gas and
oil, Tom mounted guard while the boys carried out their intention of
taking Stone into the inner room for a conference.

Stone made matters easy for all concerned by speaking first, as soon
as they all were out of earshot of Morales and Von Arnheim, and
telling the boys he had guessed their identities.

"Of course, I don't know your names," he said, "but I reckon one of
you is the son of that American bigbug old Calomares is holding
prisoner up at his ranch. And the rest of you are his pals."

Bob's face fell. He had believed their identities were unsuspected. If
this man could draw so clever a deduction, then their two other
prisoners could do likewise. Moreover, if they carried out their
original plan and went to rebel headquarters to enlist, would they not
there, too, be suspected?

"Do the others guess who we are?" he