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 asked.

“Don’t know,” said Stone.  “I haven’t been given much chance to talk to ’em, have I?  But that German is smart, and he may suspect.  But”—­and with this statement he set at rest a part of Bob’s fears—­“my bed is pretty close to this room an’ I have pretty good ears.  I overheard some things that Morales and Von Arnheim couldn’t hear, especially when you used the radio to call your father.  Anyhow, I thought it was your father.  Mostly you spoke in code, but I heard you call him ‘Dad’ a couple of times.”

The three chums looked at each other, nonplussed.  Stone laughed.

“Until I made out who you were,” he said, “I thought you were some wild-eyed kids looking for adventure an’ comin’ to the right place to find it.  But once I got a suspicion, it was easy to figure out the rest.  You see, I knew about your owning the airplane that Von Arnheim stole, an’ about your radio stations.  When you started the generator that showed me you knew something about radio, an’ that was another clue.

“So I just put two an’ two together.  Anyhow, it finally came to me who you were.  Am I right?”

“Yes,” said Jack, taking the initiative as Stone concluded, “you are correct.  It is my father who is held prisoner by the Mexicans, and these are my chums.”

Jack regarded the other searchingly.

“We’re in trouble,” he said, simply, “and we need help that you could give us.  How closely are you tied up with the rebels?  You’re an American and we are Americans.  Does that mean anything to you?”

“Yes, kid, it does,” said Stone.  Despite the fact that he was only seven or eight years older than the three chums, he had led a roving life that had given him a world of experience and an older viewpoint, and he persisted in regarding them as youngsters.  “I’m strong for the good old U.S.A.,” he continued.

“But don’t get me wrong.  These are fine people down here, and don’t you believe they ain’t.  Their standards aren’t American standards either in manners or politics.  But, just the same, they’re good folks, and don’t you let anybody tell you different.  I wouldn’t turn against them for anything.  So, although your fathers have lots of money”—­here he looked fixedly at Bob, who felt uncomfortable remembering his father’s authorization to offer Stone money to help them—­“well, don’t offer me any, that’s all.”