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 grasp the situation.”

Stone slapped his leg.

“I see what you mean,” he said.  “Your friend Jack could call the ranch, too, and interfere so much that Morales’ message would be all twisted up.”

“That’s it,” said Frank.  “And when it comes to thinking quickly and acting at once, you can count on Jack.  Just the same,” he added, “he can’t keep that up forever, and when he lands—­”

“Which he’ll have to do shortly,” interrupted Stone, “because the ranch is only fifty miles from here.”

“Why, then,” continued Frank, “these fellows can get their warning to the ranch and the boys will be captured, or at least their plan to rescue Mr. Hampton will be spoiled.  No, sir, we’ll have to wreck the radio plant here to give them a chance.  If Jack has been able so far to interfere with the warning, and we put this plant out of commission now, they may be able to carry out their rescue after all.  Let’s see.  How will we go about it?”

Both had been so engrossed they had failed to notice a dark form which, after creeping noiselessly up the slope, had started edging across the little plateau.  Now this form suddenly straightened up and leaped forward.  Frank cried out in alarm and jumped sideways, just as a spurt of flame split the darkness.  The bullet sped by, leaving him unharmed.  Stone, who was closer and stood with back turned, whirled about.  The charging form cannoned into him, and he went down.