ng. It's all based on an idea you gave me."

"What idea?"

"You told me the results of your research on the androids would be
valuable to whoever built them--as a guide to perfecting androids that
wouldn't die under earth conditions."

"That was obvious logic."

"And it ties in with another thought. A race of beings as advanced as
these could take us over without trouble, it would seem."

"Quite true. Except--"

"Except that they themselves may not be able to exist on earth, either;
no more so than we could exist on the moon without creating conditions
favorable to our physical capabilities."

"So ...?"

"So I'm betting that the ten androids were sent here on a
trial-and-error basis, with the objective of perfecting them and
creating an android army to move in and take us over."

"It's a thought, but with their power they could achieve the same result
with less effort by pulverizing us. Or so it would seem to me."

"True, but maybe they don't want us pulverized; maybe they'd rather take
over a working planet than a lot of rubble."

"All that follows logically," Entman admitted, "provided the original
hypothesis is true--that they cannot invade us in person."

"Right. But I've got to start somewhere and hope I'm on the right
track."

"One thing occurs to me. Eight of the androids died and one was killed.
What if all ten had succumbed? How did they plan to get their data?"

"Who knows? I'm not saying the idea is foolproof. But a certain amount
of risk had to be involved. If the ten died, they would have missed.
Maybe they'd try again in that case. But they were lucky--one survived."

Entman was peering thoughtfully at nothing. "Your idea is bolstered by
the fact that the androids were found all over the country. They could
have been testing various climates."

"But it's weakened by the creatures being found in cities--the least
likely places to escape detection. Why didn't they stay in isolated
sections?"

Entman smiled. "I like the way you reach out for arguments against your
own theory, but you reached too far for that one. If they'd done that,
who would find the androids and do the research work?"

Brent Taber brightened. "You comfort me, Doctor. That little thread got
lost in my maze. They wanted the creatures to be found. They didn't
expect to fool us. Why else would the one in Chicago go brazenly into a
tavern, start to drink and then get into an argument?"

"That's right. The argument must h