ontinue their journey, and this should bring them to the Calomares
ranch on the morning of the second day.

"Time to get ready," said Mr. Temple, looking at his watch. "And,
remember, the very first thing you must try to do is to get into their
radio station and call me. Day or night, the men here will be watching
for your signal and will call me. I'll be mighty anxious about you. So
remember."

"We shall call you, sir," said Jack, as the boys moved away. "And
don't worry. I'm sure we'll come out all right."

CHAPTER XVI

A SOUND IN THE SKY

"Good-bye, Tom."

"S'long, Jack."

"Keep a watch for our signal. We'll call you."

"I will that. An' if it's in trouble you are, Dave an' me'll be ridin'
just as fast as we can to help you. Wish you'd let me go 'long. I'm
half minded to follow you."

"No, no. We'll stand our best chance alone. They won't suspect we're
other than a bunch of wild young fellows out for adventure."

Tom grumbled, but the force of the reasoning was apparent to him. They
leaned from their horses for a last firm handclasp, then Jack rode on
to join Bob and Frank who sat on their horses some distance ahead.

"You're the boy to give it to 'em, Jack," called the big ex-cowboy in
a last farewell. "Give 'em thunder."

Jack waved a parting salute as he joined his comrades. Frank and Bob
did likewise. Then with night settling down over the vast desert waste
they rode on into old Mexico.

Beside the white stone marking the international boundary, Tom Bodine
sat his horse like a statue. Moodily he watched until they were out of
sight. It was a hard life Tom had led in his day and when he took the
job at the radio plant it was with a sigh of relief at the ease ahead
of him. But now despite his fifty years, the last thirty of which had
been filled with hard knocks, he felt the old call to adventure urging
him on.

With drooping head, he turned his horse toward home. But hardly had
the animal started forward, than he dragged it about again.

"Let's go," he shouted to the empty silence, and whirling his sombrero
aloft, brought it down on his horse's flank. Then he rode on after the
three figures that had been swallowed up in the darkness.

Far ahead of him, for Tom had taken considerable time to reach his
decision, rode the three companions. The young moon shed only a wan
and wraithlike radiance over the plain. They were alone, and the
parting with their last friend, combined with the solit