Somewhat startled, but glad to know the youth, and more than willing to talk with him on the subject mentioned, Evan Harwich tried to smile encouragingly. It wasn't too easy, considering his weathered, space darkened features and threatening size; but he did his best. "Pleased to meet yuh, Arnold," he said rather clumsily, offering a big hamlike hand. "I wanted to talk to you too. How about a drink and a quiet corner, where the crowd here won't be stepping all over us?" They retired to a table in a screened nook. "Now," said young Arnold, "you've seen as much of the Forbidden Moon as anybody alive, Harwich. You must know that the energy aura around her is real and not a fable. You must know, too, that it couldn't be a natural phenomenon, since nothing in nature acts like it does. There's only one alternative possibility as to what could cause it! Even though Io seems so deserted, somehow there are machines there, functioning to maintain that shell of force! Right?" Harwich nodded. Little glints of intense interest seemed to show in his eyes. "I've believed that for a long time," he admitted. "But those machines must be plenty wonderful to build up a barrage of invisible energy, thousands of miles in extent! Our scientists couldn't even begin to dream of doing anything like it! Even the principles employed must be a million years ahead of our time!" "Right again!" the boy responded. For a second he cast a guarded, suspicious glance around the room, where Earthmen and leathery Martians were talking and laughing and drinking. "The evidence can't be disputed," Paul Arnold whispered at last. "It might be that the people who invented those machines have been extinct for ages. But the mechanisms they created are still operating. There's superscience there on Io, Harwich! How much could we benefit civilization, if we could somehow find out what the principles of those machines are? How much damage might be done if those principles happened to fall into the wrong hands, among men? War and conquest--a whole solar system thrown into chaos--might result!" Evan Harwich wanted to laugh scornfully, wanted to call the kid a dreamer of wild dreams; but the realization that young Arnold probably told the truth, made his hide tingle and pucker instead. "Maybe you're right, fella," he growled. "Of course I am!" Arnold almost snapped. "My father believed it for years, and his work must go on, even though the Forbidden Moon scares me plenty. You saw yourself, Harwich, that his Energy Barrage Penetrator was almost successful. I've been trying to build another, with enough power to get through." Harwich's lips curved, a nameless, wild thrill stirring in his blood. But after all, even before he'd left a great consolidated farm in southern Illinois nine years ago, to become a spaceman, he'd been an adventurer at heart.