Donald was an engineer. The engineer. Of the four, he alone knew
every inch of the physical set-up of the refinery. So?"

"Yes. That's right. But that doesn't say where--Wait a minute, though.
If he'd just shoved it in a crack somewhere in the mountains, he'd know
a detector might find it, more easily than before it was dug. He'd have
put it some where deep, deeper than he could possibly dig. Maybe in an
abandoned mine?"

"No place," said Shearing, "is too deep for us to probe. We've examined
every abandoned mine on that side of Titan. And it doesn't fit, anyway.
No. Try again."

"He wouldn't have brought it back to the refinery. One of us would be
sure to find it. Unless, of course--"

Hyrst stopped, and the tension in the sick-bay tightened another notch.
The ship lurched sharply, swerved, and shot upward with a deafening
thunder of rocket-blasts. Hyrst shut his eyes, thinking hard.

"Unless he put it in some place so dangerous that nobody ever went
there. A place where even he didn't go, but which he would know about
being the engineer."

"Can you think of any place that would answer that description?"

"Yes," said Hyrst slowly. "The underground storage bins. They're always
hot, even when they're empty. Anything hidden near them would be
blanketed by radiation. No detector would see anything but uranium.
Probably even you wouldn't."

"No," said Shearing, looking amazed. "Probably we wouldn't. The
radioactive disturbance would be too strong to get through, even if we
were looking for something beyond it, which we weren't."

* * * * *

Christina had sprung up. Now she bent over Hyrst and said, "But is there
a way it could have been done? Obviously, the Titanite couldn't have
been put directly into the bin with the uranium--if nothing else, it
would have been shipped out in the next tanker."

"Oh, yes," said Hyrst. "There would be several ways. I can think of a
couple myself, and I've never even see the layout. The repair-lift
shaft, I know, goes clear down to the feeder mechanism, and there's some
kind of a system of dispersal tunnels and an emergency gadget that trips
automatically to release a liquid-graphite damping material into them in
case the radiation level gets too high. I don't remember that it ever
did, but it's a safeguard. There'd be plenty of places to hide a lead
box full of Titanite."

"_Unless I show them how_," repeated Shearing slowly, and began to undo
t