A vermilion shaft of light pierced the semi-darkened rooms. The animal had been gone from sight not more than a minute. Abruptly something grayish white unfolded in the reflector's beam. It rapidly expanded under three pairs of bulging eyes--not the small, pinkish rat that had disappeared but sixty seconds previous, but a full grown rat, scarred and tailless as if from innumerable battles with other rats. As the current clicked off Aaron Carruthers bent forward. Too late. The rat scurried from the laboratory with a squeal of alarm. Carruthers returned to his seat before the atomic machine and sat down. His face was worried. Dark thoughts stormed his reason. The rat he had placed within the atomic ray had aged nearly two years during the minute it was out of mortal sight. Two years! He pulled a pad from his pocket and calculated the time that had elapsed since Professor Dahlgren had vanished from that same spot. Nearly forty hours. That would mean.... Nanette stirred in her chair. "What happened to the little rat, Aaron?" Carruthers, busy making calculations, did not hear the question. She turned to her brother. "Karl, what's the meaning of this? The second experiment didn't turn out like the first one. What became of that little rat?" "I don't know what happened, Nan," spoke Karl. "Now don't bother me with your silly questions. You saw the same thing I did." * * * * * Carruthers raised his head and spoke quietly. "That rat you saw materialize under the atomic rays was the same rat you saw me place within the square." "But it couldn't be," protested the girl. "Nevertheless," shrugged Carruthers. "It was the same animal--only it had aged nearly two years during the brief time interval it was off from our planet." "It's preposterous," cried the girl. "Nothing is preposterous nowadays, Nanette." "That's the woman of it," spoke Karl. "Always doubting." "You boys are playing tricks on me," retorted the girl sharply. "I shouldn't have come to your old laboratory. Just because I'm a girl...." "Don't," pleaded Carruthers, looking up from his pad of figures. "We're trying to solve the mystery underlying the forces which we have created." He replaced the test tube within the center of the square and returned to the atomic machine. Through the twilight shadows of the room glowed the strange new ray. Faintly the generator hummed. Lights sparkled and twisted around the cathode in serpentine swirls. "You needn't trouble to explain your silly experiment again," finished Nanette, rising abruptly to her feet. "I'm going home and dress for the New Year's party." "Watch your switch like I asked you to," spoke Carruthers. "Sit down," added Karl. "Don't put the rest of us in danger!" "Oh-h-h!" gasped the girl as she inadvertently stepped squarely into the atomic ray of amber-colored light. * * * * *