He sat down and began to think. He sat there for almost half an hour. Once he got up and went over and examined the openings to the ventilator pipes. He removed the screen from one of them, a pipe about two feet in diameter, and looked into the blackness of the pipe's interior. What he saw evidently satisfied him, for he smiled again and went back to resume his pensive pose. At last, he rose and with the grim smile playing on his face he went to work. He climbed up into the ventilator pipe he had examined, and started to worm his way into its dark maw. His legs kicked futilely for a moment, then he was hunching his way along through the tube. He worked his way along for a dozen yards or so, then he came to a place where the tube divided in two. He unhesitatingly chose the path to the right--he knew these tubes well enough to traverse them with his eyes shut, even though he had never seen them from the inside before. After a few yards of further crawling, he saw a light ahead and increased his speed. Before long, he was lying in front of a grating and looking out into the officer's mess-room. He could see Tarrant and Rogers. They were seated disconsolately at the table, speaking little, apparently, for Manool watched them for five minutes before he tried to attract their attention, and in all that time, Tarrant only spoke once. When Manool tapped on the grating, they looked up startled, and reached for their weapons. Rogers was unable to locate the rapping and swung about a little wildly until Tarrant pointed out the ventilator opening. Then he recognized Manool before Tarrant did. "It's the farmer," he exclaimed, in surprise. "What are you doing up there, Sarouk?" Manool beckoned them over to the ventilator. "Don't talk too loud," he cautioned in a hoarse whisper. "I can't say much. Somebody is guarding outside the door, maybe they hear me. They kill Doc Slade and the chemist. I got a scheme. You take this grating off, while I go back to the farm and get something." * * * * * He backed away without waiting for an answer and made his way slowly back to the farm. He picked up one of his boxes of tooth-powder and hoisted it up to the ventilator shaft, shoving it back as far as he could. Then he climbed in after it and began his journey back to the mess-room, pushing the box ahead of him. It was slow work, but he made it at last, and called softly to Tarrant to come and get the box. "What's this all about, Manool?" demanded the captain, but Manool refused to answer. "Can't talk too much, Captain," he whispered. "Got to hurry. If someone tries to come in farm before I get these boxes over here, this whole plan be shot. Don't you talk now, please." Tarrant nodded his understanding and Manool started back for another box of tooth-powder. As he hunched his way along, he heard Tarrant say to Rogers, quite plainly: "Think he knows what he's doing, Ike?"