“You’re making it sound like you wanted him to arrest us,” I snapped. “Because that would keep us and our scary pheromones away from the people who aren’t sick yet. Only you can’t be putting off those pheromones, since you never got an implant, and I…” I stopped, a sick feeling spreading through my stomach. “Nathan, are you saying this is all my fault?”

“No,” he said hurriedly. “No, I’m not saying that at all. I talked to Mom, at length, about the differences between chimera and sleepwalkers, because I knew I’d need to explain them to you—and I really think I should do as much of it as I can. Mom isn’t good at talking to people who aren’t geneticists.”

“You’re not a geneticist.”

“No, and sometimes she loses me. But you’re not giving off the pheromone tag that the sleepwalkers use to activate each other. She said it’s like comparing a can of spray paint to a master painter’s brush. You can get art out of either one, but one will tend to be much more focused and refined. The sleepwalkers are putting off a chemical stew that says everything from ‘hey, do what I’m doing, this is neat and you should try it’ to ‘eat here, here, eat.’ She’s still trying to analyze the specific pheromones that you and the other chimera put off. As near as she can tell, they say ‘listen to me, I am bigger than you, and you should listen.’ You may eventually be able to use them to accomplish just that. You may be able to make them listen.”

I looked at my bandaged wrist, the white barely visible through the gloom. “Are all the sleepwalkers going to listen with their teeth?” I asked glumly.

“Only the ones who are already too brain-damaged from the integration process to understand the message. I think they’re all going to want to be close to you. Some of them may even have the intelligence to obey when you give them simple orders, like ‘stop’ or ‘don’t eat me.’ But some of them are going to be too far gone, because the integration process involves far too much brute trauma to the host. They don’t have the superstructure necessary to process complicated information.”

I wrapped my arms around myself, hunching over in my seat. “This just keeps on making me feel worse and worse. Every time I think I’m okay with not being human, you come up with some new fun fact, like ‘hey, Sal, you’re basically a bug zapper for sleepwalkers, hope that’s okay with you.’ ”

“I’m okay with you not being human,” said Nathan. “However long it takes for you to be okay with it, I will wait for you. We’re going to figure this all out together.”

“But you still think that cop should have arrested us.”

“Yes,” admitted Nathan. “At the very least, he should have questioned us more about why we’d decided to load ourselves and the dogs into the car when you were clearly injured, instead of going to a hospital. I think…” He took one hand off the wheel as he reached up and adjusted his glasses, and I suddenly realized the car was moving: had been moving for some time. I’d been so distracted by arguing with him that I hadn’t even noticed. Finally, he sighed, and said, “I think things are getting very bad, very quickly, and I think that officer knew about it. He made a threat assessment. He decided we were not dangerous. As luck would have it, he was right, and it was definitely the choice we wanted him to make. I’m just worried about how many times people will make that same choice tonight, and how many times they’re going to be wrong. It’s too late to stop the outbreak. That doesn’t mean we need to help it spread faster than it has to.”

I bit my lip again, frowning. I couldn’t make out the details of Nathan’s face, and I was glad; I didn’t want to know whether he was wearing his mother’s look of calm resignation, like talking about leaving people locked in what was about to become a plague zone could ever be interpreted as a good thing. The landscape rushing by outside the car windows was a bruised blur that echoed my mood: purple and gray and somehow threatening.

It was nice to know that a good scare that had nothing to do with being in a car could distract me from the fact that I was in a moving vehicle. Maybe I just needed to get a portable DVD player and start watching horror movies whenever I had to go somewhere.

I wanted to let the matter lie—I really did—but there was one more question I needed to ask before I could do that. “How many people do you think are going to die?”

There was a long pause before Nathan answered me. “A lot,” he said, finally. “From both sides. I think a lot of humans are going to die, and a lot of the ones who don’t are going to take powerful antiparasitics and kill their implants—and they’d do it even if we had evidence that the tapeworms have achieved rudimentary sapience in their isolated state, and should hence be treated as thinking beings. People have fought long and hard to have the right to control their own bodies in this country. They’re going to view the implants as dangerous intruders. And the sleepwalkers… maybe there’s some kind of treatment that can give the tapeworms that have taken their hosts over a better existence, something closer to what you and Adam have, or at least closer to what Tansy has. But for right now, we have to treat them as if they were already dead.”

“Do you think that would work?”

“Honestly, I don’t know. Most people—human people—are going to be very upset when they find out what’s going on. Even if there is a treatment, it might be a long time before it can be put into practice, if ever.”