The agtech dumped another load of algae into the trough. "I couldn't say." She tapped her forehead. "It's the wetware. If you want to talk shop, that's fine. Otherwise, I can't."

"I see." Elin dabbed a toe in the warm water. "Well, why not? Let's talk shop."

Someone was moving at the far edge of the island. Elin craned her neck to see. The agtech went on methodically dipping her net into the lake as God walked into view.

"The lake tempers the climate, see? By day it works by evaporative cooling. Absorbs the heat, loses it to evaporation, radiates it out the dome roof through the condensers."

Coral was cute as a button.

A bowl of fruit and vegetables had been left near the waterline. She walked to the bowl, considered it. Her orange jumpsuit nicely complemented her cafe-au-lait skin. She was so small and delicate that by contrast Elin felt ungainly.

"We also use passive heat pumps to move the excess heat down to a liquid-storage cavern below the lake."

Coral picked up a tomato. Her features were finely chiseled. Her almond eyes should have had snap and fire in them, to judge by the face, but they were remote and unfocused. Even, white teeth nipped at the food.

"At night we pump the heat back up, let the lake radiate it out to keep the crater warm."

On closer examination-Elin had to squint to see so fine- the face was as smooth and lineless as that of an idiot. There was nothing there; no emotion, no purpose, no detectable intellect.

"That's why the number of waterfalls in operation varies."

Now Coral sat down on the rocks. Her feet and knees were dirty. She did not move. Elin wanted to shy a rock at her to see if she would react.