After voicing his request that Jack put his mind to work to evolve some plan for rescuing Bob, Frank picked up the headphones and idly clasped them to his ears, and sat silent, gloomily regarding the instruments on the table, although in reality not seeing them. By some chain of thought, he was once more back on Long Island, standing on the lawn of the Temple home, and watching for Della to emerge from the doorway. It seemed to him, so powerful was the impression, that he had arrived to tell her Bob had been slain in the Sacrificial Games in Athensi, and—— “Jack,” he cried suddenly, in so startled and excited a voice that his chum, sprawled on the grass, leaped to his feet. “My—my—” Words failed him, his face grew white as a sheet, and his eyes seemed actually to bulge out of their sockets. “What is it?” demanded Jack, anxiously. “Are you sick? Speak. Tell me what’s the matter.” Frank could only wave his hands feebly and shake his head. Then he seemed to change into new life under Jack’s gaze. Color returned to his cheeks, his eyes grew bright and joyful, and, leaning forward, he drew the telephone transmitter toward him and began to speak. In Jack’s mind, stupefaction succeeded bewilderment as he listened. CHAPTER XX. AN OLD FRIEND APPEARS. “Mr. Hampton isn’t here, but this is one of his men speaking,” Jack heard Frank say. As in a daze, Jack stood open-mouthed while Frank continued: “What’s that? Roy Stone?” Frank’s voice was joyful, unbelieving. “I can’t believe it’s you, Stone. I just can’t,” Frank continued. “This is Frank Merrick speaking. But how in the world? Where did you come from? Wait a minute, wait a minute.” He turned to Jack. “It’s Roy Stone,” he cried. “Remember?” Did Jack remember? A flood of memory engulfed him. All the details of that fight in the cave a good four years before came sweeping back. Mr. Hampton had been held prisoner by Mexican rebels in a stronghold in Old Sonora, across the border from New Mexico. The rebels also had stolen the airplane which was the pride of Bob and Frank, who were its joint owners. Setting out with Tom Bodine, an ex-cowboy, to rescue Jack’s father, the three boys had put up one night in a mountain cave to which Tom led them. They found it outfitted as a radio station by the Mexican rebels. Shortly after their arrival, one of the Mexicans named Morales, a German named Von Arnheim, who was stirring up trouble on the border in the hope of embroiling the United States in war, and a young American aviator named Roy Stone, a stormy petrel, a soldier of fortune, who had cast in his lot with the rebels, arrived. More to the point, they arrived in the airplane stolen from the boys.