"Tom! Someone has stolen your invention" gasped =BudBarclay as he scanned a news story on the front page of the =Shopton Bulletin! =TomSwiftJr, a crew-cut blond youth of eighteen, looked up in astonishment from a blueprint he had just taken from the office file. "Stolen my invention" =Tom echoed? "Which one?" "Your new machine for extracting helium from the air!" =Bud jumped up from the leather armchair in which he had been seated and thrust the paper in front of his chum. =Tom frowned at the news item. It was headed: French Scientist Invents Revolutionary New Helium Source! With growing excitement, =Tom read the story. The next day =Tom ate a hurried breakfast, kissed his mother and =Sandy good-by, and drove to the plant with his father. Both shared a feeling of stifled excitement. If the =Swifts were assigned the manned space flight to =Venus, it would be the most daring venture they had ever undertaken! =Bud met them on the Enterprises airfield, eager for the trip ahead. A =Swift jet plane stood ready for take-off on the runway, and within half an hour they were landing in =Washington. At =NASA headquarters Dr =LarsNorstrom, a lean man with Viking blond hair, greeted them warmly. "Thanks for coming on such short notice," he told the =Swifts as he shook hands. Dr =Nordstrom, coordinator of the national space flight program, was an old friend of the =Swifts. With his mind still on his work, =Tom stared at the quivering cowpoke. "Fireworks! =Chow, what are you talking about?" =Chow grabbed =Tom by the arm. "Come see for yourself, boss," the cook begged! "Brand my space spinach, it's plumb spooky! Either the galley's haunted, or them Martian pals o' yours is playin' some kinda joke on us!" =Chow was referring to the =Swifts' mysterious friends from Planet X with whom the =Swifts had been in communication for many months. =Tom and =Chow ran down the corridor to the private galley. At the cook's request, it had been installed in the lab building so he could "whomp up" special meals for his beloved young boss whenever =Tom was hard at work on a new invention. "Resigning?" =Tom stared at =Bud. "Are you serious?" "I'm dead serious," =Bud declared as he parked himself on a high stool. "But why," =Tom persisted? "Don't you realize this is an honor? You'll be the first space pilot from earth to make it to another planet!" =Bud's answer was a stubborn shrug. He seemed to be groping for words to express whatever was troubling him. "It's not only an honor, it's a government request," =Tom went on. "This isn't just a private job your doing for =Astro-Dynamics. It's a project undertaken in our nation's interest!" "Sure, sure, I know." =Bud squirmed uncomfortably. "Then what's your problem?" "My copilot, that's what," =Bud blurted out in exasperation. "The guy's an absolute pain!" "No sense wasting time guessing," =Tom murmured. He picked up the room phone and dialed a plant number. "Hi, =Jack. This is =Tom," he said when a voice answered. "Got a lock job for you here at my lab." "Sure thing, =Tom. Be right over." =Jack, a dark-haired man of thirty-five, arrived in the hall a few minutes later carrying a satchel of tools. Slender and stoop-shouldered, with long sensitive looking fingers, =TurnbridgeJackson was the expert locksmith of =Enterprises. His almost uncanny ability with locks and electronic-eye devices had earned him the nickname of "Open Door =Jack." More than once, outside firms had called him in to crack the combination of safes or vaults. The concussion from the laboratory blast bowled the youths over. =Bud struck his head against the wall, and =Tom was hurled along the corridor. "Boss! Boss! Are you all right?" =Chow's voice seemed muffled, as if he were shouting through layers of cotton batting. =Tom shook his head, trying to clear his brain. "I'm -- I'm all right." =Tom struggled up, with =Chow helping him. "Better see about =Bud!" As the cook hurried to =Bud's prostrate form, =Tom saw =HarlanAmes running up the hall. He was white faced with anxiety. "Thank heavens you're all right, skipper," he panted! "And you =Bud?" "The thief who has been rifling my lab," =Tom thought angrily! "Looks as though =Bud was right about my helium machine plans being pirated." It was hard for =Tom to distinguish much about the phantom intruder through the peephole. The reflected glow of the man's flashlight only partly revealed his figure. But he appeared to be tall and slender. His face was hidden by the mask an his hair was concealed by a dark hat pulled low over his forhead. =Tom's first impulse was to rush in and overpower the man. But after pondering a moment, he decided on another course of action. =Tom's eyes flicked back and forth from his wrist watch to the pressure dials on the machines. He had mentally calculated the amount of Durabuoy needed to lift the weight of the aluminum igloo. "Should be about ready, =Dad," he whispered! "Let's unscrew those last two floor bolts." Mr =Swift nodded, a smile of excitement playing about his lips. "Dad's actually enjoying this tight spot we're in," =Tom thought with admiration! He and his father picked up wrenches and moved to opposite sides of the laboratory. =Tom had attached a Durabuoy sphere by a bracket to the wall above each of the two remaining floor bolts. For an instant =Tom stared unbelievingly at the screen of the prober as the speeding sedan forced the truck off the road. "Those thieves are after my helium machines," he said to himself! "=Furster's henchmen, I'll bet!" Desperately, =Tom tried to think of a way to prevent the valuable devices from falling into the hands of his enemies. He dashed to the wall and pressed an alarm button while his eyes raked the observatory room. "I must do something -- and fast," =Tom thought! Suddenly he noticed that one of his small repelatrons was lying in a corner. "What a break," =Tom muttered! "Maybe there's a chance I can stop those hijackers!" "Oh, =Tom," =Sandy cried, coming over to stand beside her brother! "I know something must be terribly wrong! =Bud's had an accident!" "Lieutenant =Holbrook only said he'd been taken ill, dear," Mrs =Newton ventured. "Perhaps it's just the effects of weightlessness, now that the astronauts are on their way." =Tom hated to add to everyone's fears, especially =Sandy's, but he shook his head. "=Bud has been on too many space missions to suffer nausea or disorientation from that cause." =Tom clenched his fists. He felt a desperate need to take action, now that his chum was in possible danger. "Dad, I'm goin after =Bud in the =Challenger," =Tom blurted out suddenly! Mr =Swift laid a hand on is son's arm. "Steady, boy. We'll have to be patient until we know more of what's going on."