At the instrument panel, he checked his position. With a little luck, he might reach Terra before the thing got through to him. It depended on how rapidly it was growing. As he strained to hear, a sort of sucking sound came from it now as it worked behind the barricade. His audio-visor suddenly flickered and hummed. Who would be calling him? Only someone on Caliban. His father? But why? Unless.... The face rippled onto the screen. His father's face--but it seemed that the face had aged twenty years since the interview short hours before. "Dirk," the voice said. "Dirk--have you checked your ship?" He pushed the talk-back. "Yes, dad. There's something ... something that looks like jelly. It's growing. The disinteray doesn't stop it." "You've got to turn back, Dirk. Nothing will stop that jelly-thing. As long as it gets oxygen, it'll keep growing! You've got to turn back to Caliban." Dirk's eyes flickered to the gauges on the panel. "There's not enough fuel to get me back to Caliban. I can feel the pull of Terra's solar system already." The visor went abruptly blank and then Tabor's face replaced his father's on the screen. "Listen to me, Dirk," Tabor said, and the academic hesitancy had been discarded for a terrible urgency. "That stuff in your ship is wild cells. They're the only life on Caliban. Oxygen has a peculiar effect on them. Makes them multiply by geometric progression. Do you understand that?" "I understand." Dirk's voice was a thing remote from him, apart. "There's nothing you can do to stop that growth. The disinteray won't help. You've got to get it back to Caliban--out of oxygen." "I can't. I haven't enough fuel, Tabor." Dirk fought to keep his voice controlled and calm, but he could see already a crystalline ooze seeping under the desk, the filing cabinet. It couldn't be stopped. "Can you reach Terra?" Tabor's face was knit into a perplexed maze of wrinkles. "I might, if the thing doesn't grow too fast." Tabor nodded. "If you get through to Terra, you'll live a little longer at least." "What do you mean--a little longer?" Tabor's face seemed to fill the screen and his eyes caught and held Dirk. "Don't you see? Even if you get out of the ship on Terra, the thing will follow. There'll be no stopping it. Eventually, it will engulf the whole earth." "No!" Dirk's voice was a hoarse whisper. "No!" "There will be nothing to stop it there. It will have all the oxygen it needs. I didn't know you were taking off. I'd have warned you. It's my fault." Tabor's voice trailed away and again the visor went blank. "No," Dirk said softly. "It's my fault. All my fault. Not only have I failed dad, but now I'm going to destroy Terra." He stared at the slime as it inched with increasing speed across the cabin. The sucking, bubbling noise was quite dear now. * * * * *