"Kalson!" he screamed at them. "He's following me! He's dead! I killed him once! But he's here! I'm going to open the port and let the air out! Then Kalson won't follow me. I'll kill him again! Then I won't see him crawling ... and crawling...." He wheeled and ran down the corridor. "It's Wrymore!" gasped Captain Wallace. "I thought he'd gone with the rest. Come on! We've got to stop him!" The three raced down the corridor after the madman, who had disappeared into the main passage leading to the 'midships airlock. They reached the corridor together and wheeled into it. There at their feet lay Wrymore--they almost fell over him. Markoe turned the man over. "He's dead!" he exclaimed. "What could have--" "Fright, I suppose," said Wallace. "Look." * * * * * They followed his gaze along the corridor. There, on the deck in the center of the passage, slender, mobile tip questing and probing, lay one of the flame-things. Markoe and the captain drew their pistols, but Cargyle, who had already one experience with these glowing enigmas, seized their arms. "It's no good," he whispered. "Come away. It's no good. You can't hurt them." "Well, by the Star of Saffta, I'm going to try," retorted Wallace, and he swung up his gun. The next moment the cavernous passage-way roared and trembled to the blaster's discharge, and the hissing uproar was intensified as Markoe fired in turn. The flame-thing sprang upright--grew longer--towered high above them. "Run!" snapped Cargyle, diving into the side passage. But the other two, struck with astonishment, stood where they were. Cargyle, peering cautiously around the corner, saw that ominous, dead-black ring in the flame-thing's middle. Before he could draw back the intense and brilliant beam sprang out of the black ring, but this time it struck at Wallace and Markoe, and Cargyle, although momentarily blinded, was not subjected to the tearing pain that had snuffed out his consciousness. When he could see again, he perceived his companions sprawled on the deck--to all appearances, dead. Their attacker was again pursuing its endless testing of the floor. Would the thing strike at him if he went to his companions' assistance? Cargyle shrugged. He'd have to take that chance. Cautiously he moved out into the passage. Except for a noticeable increase in the rapidity of the pulsation of its shifting colors, the flame-thing ignored him. As quietly as possible he dragged first Captain Wallace and then the astrophysicist back into the shelter of the side passage. What in God's Name were these flame-things, Cargyle wondered. They appeared to recognize and resent attack. They _must_ be alive! Where had they come from, and was Markoe right? Were they slowly destroying the _Denebola_?