"I stepped up the humidity and temperature controls," I told her. She
nodded in quick comprehension, but I went on for Muller's benefit.
"Trying to give the plants the best growing atmosphere. We'll feel
just as hot and sticky when the carbon dioxide goes up, anyhow."

"It must already be up," Wilcox said. "My two canaries are breathing
faster."

"Canaries," Muller said. He frowned, though he must have known of
them. It was traditional to keep them in the engine-room, though the
reason behind it had long since been lost. "Better kill them, Mr.
Wilcox."

Wilcox jerked, and his face paled a bit. Then he nodded. "Yes, sir!"

That was when I got scared. The idea that two birds breathing could
hurt our chances put things on a little too vivid a basis. Only Lomax
seemed unaffected. He shoved back now, and stood up.

"Some tests I have to make, Captain. I have an idea that might turn up
the killer among us!"

I had an idea he was bluffing, but I kept my mouth shut. A bluff was
as good as anything else, it seemed.

At least, it was better than anything I seemed able to do. I prowled
over the ship, sometimes meeting Peters doing the same, but I couldn't
find a bit of evidence. The crewmen sat watching with hating eyes. And
probably the rest aboard hated and feared us just as much. It wasn't
hard to imagine the man who was behind it all deciding to wipe one of
us out. My neck got a permanent crimp from keeping one eye behind me.
But there wasn't a shred of evidence I could find.

In two more days, we began to notice the stuffiness more. My breathing
went up enough to notice. Somehow, I couldn't get a full breath. And
the third night, I woke up in the middle of my sleep with the feeling
something was sitting on my chest; but since I'd taken to sleeping
with the light on, I saw that it was just the stuffiness that was
bothering me. Maybe most of it had been psychological up until then.
But that was the real thing.

The nice part of it was that it wouldn't be sudden--we'd have days to
get closer and closer to death; and days for each one to realize a
little more that every man who wasn't breathing would make it that
much easier for the rest of us. I caught myself thinking of it when I
saw Bullard or Grundy.

* * * * *

Then trouble struck again. I was late getting to the scene this time,
down by the engine room. Muller and Bill Sanderson were ahead of me,
trying to separate Hal Lomax a