wasn't time. Thirty or forty minutes of breathing. No tools. A steel
hull. The airlocks were naturally arranged for the greatest possible
safety under normal conditions. In every airlock it had naturally been
arranged so that the door to space and the door to the interior could
not be open at the same time. That was to save lives. To save air, it
would naturally be arranged that the door to space couldn't be opened
until the lock was pumped empty.

That in itself could be an answer. Joe said sharply, "Hold it, Chief!
Somebody watch Sanford! All we've got to do is find which lock he came
out of. He couldn't get out until he pumped it empty--and that unlocks
the outer door!"

But Sanford laughed once more. He sounded like someone in the highest of
high good humor.

"Heroic again, eh? But I took a compressed air bottle in the lock with
me. When the outer door was open, I opened the stopcock and shut the
door. The air bottle filled the lock behind me. Naturally I'd fasten the
door after I came out! One must be intelligent!"

Joe heard Brent muttering, "Yes, he'd do that!"

"Somebody check it!" snapped Joe. "Make sure! It might amuse him to
watch us die while he knew we could get back in if we were as smart as
he is."

There were clankings on the hull. Men moved, unfastening the lines which
held them to the hull to get freedom of movement, but not breaking the
links which bound them to each other. Joe saw Haney go grimly back to