Someone stepped quietly into the elevator, looking back at the search party in bemusement. When he saw her, he jumped. "Goodness, you scared me!" He blinked his long lashes, regarding her masked face, then looked down at his own tailcoat. "Oh, dear.

Wasn't this party white tie?"

Tally's breath caught, her mouth went dry. "Peris?" she whispered.

He looked at her closely.

"Do I…" She started to reach out, but remembered to press back flat against the wall. Her muscles were screaming from standing on tiptoe. "It's me, Peris."

"Here, piggy, piggy!"

He turned toward the voice down the hall, raised his eyebrows, then looked back at her.

"Close door. Hold," he said quickly.

The door slid shut, and Tally stumbled forward. She pulled off her mask to see him better.

It was Peris: his voice, his brown eyes, the way his forehead crinkled when he was confused. But he was so pretty now.

At school, they explained how it affected you. It didn't matter if you knew about evolution or not-it worked anyway. On everyone.

There was a certain kind of beauty, a prettiness that everyone could see. Big eyes and full lips like a kid's; smooth, clear skin; symmetrical features; and a thousand other little clues.

Somewhere in the backs of their minds, people were always looking for these markers. No one could help seeing them, no matter how they were brought up. A million years of evolution had made it part of the human brain.

The big eyes and lips said: I'm young and vulnerable, I can't hurt you, and you want to protect me. And the rest said: I'm healthy, I won't make you sick. And no matter how you felt about a pretty, there was a part of you that thought: If we had kids, they'd be healthy too. I want this pretty person….

It was biology, they said at school. Like your heart beating, you couldn't help believing all these things, not when you saw a face like this. A pretty face. A face like Peris's.