Professor Jerome Mortenson, hunched over the work bench in his private laboratory, looked around suspiciously at the sound of stealthy feet behind him, and found himself looking into the cold, unwavering muzzle of an automatic. The masked, midnight intruder who held the weapon in a steady hand, halted abruptly in his tracks and crouched tensely. He breathed hard, making the only sounds audible in the instrument-filled room. "Stand up, professor!" the intruder said coldly. "Don't try anything!" Mortenson eyed the man calmly from head to foot, his gray, penetrating eyes trying hard to see behind the polka-dotted 'kerchief that hid the fellow's features from the bridge of his nose downward. All that he saw, however, were a pair of beady eyes, flashing with deadly earnest, a muscular figure that filled a well-cut brown suit, polished black oxfords and a white flannel cap, the latter pulled rakishly down over the right temple. The man's eyes fascinated him for a moment. A devilish light seemed to radiate from them with almost stunning force. They gave him the aspect of a dangerous man. "What do you want?" Mortenson grumbled, appraising him. The intruder chuckled softly, never once removing his steady gaze from the apprehensive features of his victim. He fumbled into a side pocket of his coat and brought out a scrap of wrinkled newspaper which he handed to the scientist with an insolent shrug. "You should have had better sense, professor," he said coldly, "than to tell the world that you had discovered a way to penetrate and enter the Fifth Dimension!" Mortenson reached out for the paper, a startled look in his eyes now. His hand trembled suddenly as he unfolded the clipping and glanced over it. "I presume you refer to my interview with the editor of the _Journal_?" he inquired, controlling his anger and fear. "What has that to do with you?" "Plenty!" the fellow snapped, advancing a step. "I want the apparatus you used to enter the Fifth Dimension!" "You must be crazy," Mortenson gasped weakly. "You could never make use of it!" The intruder grunted and Mortenson heard the click of the safety catch as the man's thumb slid along the side of his automatic. "That's where you come in!" he said curtly. "You're going to see that I _can_ make use of it." "What do you mean?" the scientist asked innocently. "You know what I mean!" the man hissed sharply. "Don't try to pull that _innocent_ stuff on me. You're going to hand over your Fifth Dimensional apparatus with instructions on how to use it. Now hop!" "You don't know what you're doing," Mortenson argued desperately. "You must be insane!" "Don't I?" the man jeered. "What do you think I came here for?" "The apparatus, of course," said Mortenson, glancing about him furtively in search of a handy hammer or a weapon, "but, good Lord, man, you must be fond of trouble!" "I'm used to it!" the intruder snarled. "And I'm giving you two minutes to hand it over!"