two latticed towers of familiar construction, and between
them overheard the strands of the antenna. The Germans, Stone earlier
had explained, had built the towers in such fashion that the crest of
the hill hid them from the plain on one side while they were so far
back from the edge of the flat plateau crowning the hill as to be also
hidden from view from the valley.

Whispering an injunction to Frank to follow close at his heels, Stone
crawled on hands and knees to the fissure in the rocks down which led
the wires of the hook-up. It was not a straight descent into the cave,
and no light came from it. But the two knelt in the darkness and put
their heads close to the black opening to listen.

A murmur of speech could be heard distinctly, coming up through the
hole. Frank could not distinguish the words, but with his limited
knowledge of Spanish he was able to decipher that language was being
employed.

"What is it?" he whispered to Stone. "Can you hear? Are they speaking
in Spanish?"

"Silence. Just a minute," answered Stone.

His voice was anxious. Frank obeyed the command. In a moment, Stone
lifted his head and said hoarsely:

"It's Morales. He and the German must have overcome your friend in
some way. And I think he's got the Calomares ranch on the phone and is
giving warning that your friends are on the way."

Frank groaned.

"Then when Jack and Bob land, they'll be surprised and captured. Oh,
can't we do something?" Excitedly he jumped to his feet. "Let's put
the radio out of commission."

Stone also leaped up and laid a restraining hand on his arm.

"No, no. Wait a minute. The damage is done already. These fellows
already have given sufficient warning to put them on guard at the
ranch, even though they can't have told the whole story."

They stood undecided, looking at each other, in the starlit darkness.
With an exclamation, Frank seized Stone by the arm. In his excitement,
he shook it.

"Jack and Bob both clamped the headpieces on when they left in the
airplane," he said. "And Jack tuned the radio to the pitch of this
station, in order to be able to call us after rescuing his father.
Why, he must have heard Morales give his warning! Yes, sirree. Why
this isn't so bad!"

In their relief, the two laughed a trifle hysterically. In a moment,
however, Frank sobered again.

"Just the same," he said, "the ranch would get the warning, unless--"

"Unless what?"

"Unless Jack was quick enough to gr