"That's good--it makes lots of people pretty sick. In fact, some folks get awfully sick and can't seem to get used to it at all. It's the canals in the inner ear that do most of it, you know. However, if you're as well as that already, you'll be a regular spacehound in half an hour. I've been weightless for weeks at a stretch, out in the _Sirius_, and now I've got so I really like it. Here, we'd better keep in touch." He found her hand and tucked it under his arm. "Stabilize our positions more, besides keeping us from getting too lonesome, here in the dark," he concluded, in a matter-of-fact voice. "Thanks for saying 'us'--but you would, wouldn't you?" and a wave of admiration went through her for the real and chivalrous manhood of the man with whom she had been forced by circumstances to cast her lot. "How long must we stay here?" "As long as the air lasts, and I'd like to stay here longer than that. We don't want to move around any more than we absolutely have to until their rays are off of us, and we have no way of knowing how long that will be. Also, we'd better keep still. I don't know what kind of an audio system they've got, but there's no use taking unnecessary chances." "All x--I'm an oyster's little sister," and for many minutes the two remained motionless and silent. Now and then Nadia twitched and started at some vague real or imaginary sound--now and then her fingers tightened upon his biceps--and he pressed her hand with his great arm in reassurance and understanding. Once a wall of their cell resounded under the impact of a fierce blow and Stevens instantly threw his arm around the girl, twisting himself between her and the threatened wall, ready for any emergency. But nothing more happened; the door remained closed, the cell stayed bottle-tight, and time wore slowly on. All too soon the unmistakable symptoms of breathing an unfit atmosphere made themselves apparent and Stevens, after testing each of the doors, drew the girl into a larger room, where they breathed deeply of the fresh, cool air. "How did you know that this room was whole?" asked Nadia. "We might have stepped out into space, mightn't we?" "No; if this room had lost its tightness, the door wouldn't have opened. They won't open if there's a difference of one kilogram pressure on the two sides. That's how I knew that the room we were in at first was cut in two--the door into that air-break wouldn't move." "What comes next?"