"And if, say, you became a concert pianist, the part that runs your fingers would actually spread out, take up more of the strip to meet the increased demand for finger control. But you lose something, too. The adjacent parts of the strip get crowded out. So maybe you couldn't wiggle your toes or curl your tongue as well as you could before you started practicing."

Acton falls silent. Clarke feels his arms, cradling her loosely from behind.

"I think something like that happened to me," he says after a while.

"How?"

"I think something in my brain got exercised, and it spread out and crowded some other parts away. But it only works in a high-pressure environment, you see, it's the pressure that makes the nerves fire faster. So when I go back inside, the new part shuts down and the old parts have been — well, lost."

Clarke shakes her head. "We've been through this, Karl. Your synapses just ran low on calcium."

"That's not all that happened. That's not even a problem any more, I've brought my inhibitors up again. Not all the way, but enough. But I still have this new part, and I still can't find the old ones." She feels his chin on the top of her head. "I don't think I'm exactly human any more, Len. Which, considering the kind of human I was, is probably just as well."

"And what does it do, exactly? This new part?"

He takes a while to answer. "It's almost like getting an extra sense organ, except it's ... diffuse. Intuition, only with a really hard edge."

"Diffuse, with a hard edge."

"Yeah, well. That's the problem when you try to explain smell to someone without a nose."

"Maybe it's not what you think. I mean, something's changed, but that doesn't mean you can really just — look into people like that. Maybe it's just some sort of mood disorder. Or a hallucination, maybe. You can't know."

"I know, Len."

"Then you're right." Anger trickles up from her internal reservoir. "You're not human any more. You're less than human."

"Lenie—"

"Humans have to trust, Karl. There's no big deal about putting your faith in something you know for certain. I want you to trust me."

"Not know you."

She tries to hear sadness on that synthetic voice. In Beebe, maybe, it would have come through. But in Beebe he would never had said that.

"Karl—"

"I can't come back."

"You're not yourself out here." She pushes away, spins around; she can just barely distinguish his silhouette.

"You want me to be—" She hears confusion in the words, even through the vocoder, but she knows it's not a question. "—hateful."

"Don't be an idiot. I've had more than my fill of assholes, believe me. But Karl, this is just some kind of cheap trick. Step out of the magic booth, you're Mr. Nice Guy. Step back in, you're the SeaTac Strangler. It's not real."

"How do you know?"