But the professor did not cease. For five minutes--ten, fifteen--he swung that mighty ray around, stepping up its power, lengthening its range, as it reached its invisible, annihilating arm farther and farther out.... Meanwhile Jim was radio-phoning frantically. The air seemed strangely full of static. At last he got Overton of _The New York Press_. "Carter speaking, out in Arizona," he said. "Getting any reports on the ray?" And back came the tremendous news: "Results! Man, the world's crazy! They're gone--everywhere! Tell the professor to lay off, before he sends us scooting too." "Right!" said Jim, cutting his motor. "More later!" And to Professor Wentworth he called: "All right, that's enough! That ray was stronger than you knew!" But there came no answer, and mounting to the wing-tip, Joan following, Jim saw a sight that froze him with horror. They beheld the professor, slumped against the tube, his whole body glowing a pale, fluorescent green. "Father!" screamed Joan, rushing to his side. "Oh, Father!" The man stirred, motioned her away, gasped weakly: "Do not touch me, child--until the luminosity goes. I am highly radio-active. I had no time to--insulate the tube. No time to find out how. Had to--hurry--" His voice waned off and they knew he was dead. The two stood there stunned by the realization of his great sacrifice. He and Joan had set forth on this venture knowing they stood at least a chance, thought Jim, but Professor Wentworth had known from the start that it was sure death for him. * * * * * The sun stood out above the eastern horizon like a huge gold coin, bright with the promise of life to spend, when Jim and Joan took off at last for the return home; but the radiance of the morning was dimmed by the knowledge of the tragic burden they bore. For some moments, as they winged on, both were silent. "Look!" said Jim at length. "Look ahead, Joan!" She looked, brightened somewhat. "Yes, I see." And after a moment, lifting her hazel eyes to his, she said. "Oh, Jimmy, I'm sure it means happiness for us." "Yes, I'm sure!" She stirred, moved closer. "Jimmy, you--you're all I have now." He made no reply, save to press her trembling hand. But it was enough. Silently, understandingly, they winged onward into the morning light.