“This is impossible,” muttered Nathan.

“Is it?” Dr. Cale looked at him calmly. “Nathan. You know better. You’ve always refused the implant. I know you have, I’ve seen your medical records. That tells me that you knew, on some level, just what a terrible idea it was. Maybe if there was less human DNA… but then the implants wouldn’t have worked as intended, and I wouldn’t have your lovely siblings to keep me company.”

“Maybe you wouldn’t need them,” countered Nathan. “If all this… this madness is true, you’ve been hiding since you left SymboGen because there was so much human DNA in the worms. You could have come home.”

“There would always have been something that was big enough to keep me away, Nathan. Once I started down this road, there would always have been something. You’re not as naïve as your girlfriend—no offense, Sal, you’ve done surprisingly well, given how little time you’ve had.”

“None taken,” I said numbly.

But Dr. Cale had already moved on. Her eyes were on her son as she said, “Once Steven decided he wanted me, it was already as good as over. I knew that. Your father knew it, too. That’s why he let me go. That’s why he never went looking for me, even after my association with SymboGen had been officially and publicly terminated. There was always going to be something. It might have been worse than this, it might have been a little better, but it was going to be something.”

Nathan didn’t say anything. He just glared at Adam and Tansy like he was holding them personally responsible for his mother’s defection from her life—like they had somehow made her paranoid and delusional, reducing her to hiding in a deserted bowling alley when she had been responsible for one of the greatest scientific advancements of our time.

Adam dropped his eyes, looking down at the floor like he was ashamed. Tansy, on the other hand, stepped forward, slapping her hands against her chest in a gesture that was all primate, no matter what she might claim about her mind.

“You want to dance, ass-face?” she demanded. “I don’t care if you’re Doctor C’s biological son or not, I will f**k you up so bad your own momma can’t recognize you.” She stopped, puzzlement washing her irritation away in the time it took to blink. “Wait. I don’t think that works. Doctor C? If I mangle him all up in front of you, and you watch me do it, can I actually mess him up so you can’t tell who he is?”

“No, dear,” said Dr. Cale. “Also, please do not harm my son, or his significant other. They are to be considered part of the family, and the rules for dealing with Adam apply to dealing with them. Do I make myself clear?”

Tansy sighed. “Yes, Doctor C.”

“Good.” Dr. Cale beckoned for Tansy to come and stand beside her chair. Tansy did so, glaring at Nathan all the way. “I’m sorry, dear. She’s protective of Adam, even though she’s technically the younger of the two. His integration was more complete, but hers has progressed faster, and she feels like it’s her duty to make sure that he’s safe.”

“This is… almost as interesting as it is terrifying, but what does it have to do with the sleeping sickness?” I asked hesitantly. I wanted to distract her from the subject of Adam and Tansy before things got even stranger than they already were. I wasn’t sure how much more of this I could handle. “You said that if we came here, you’d tell us about the sleeping sickness.”

The look Dr. Cale gave me was genuinely puzzled, like I’d just said something that made no sense at all. “But, Sal… that’s what I’ve been doing. Haven’t you been paying attention?”

“Adam and Tansy were given custody of the bodies they now inhabit freely and without competition from the body’s original owners. That’s part of why they were successful. When they were given their current forms, there was no one there to fight them off. To belabor the metaphor a bit, it was like taking them into an empty house and handing them the keys. People had lived there before. They’d done their damage to the foundation and chosen the paint in the upstairs hall. But those people were gone. There was nothing they could do to stop the new tenants from moving in.” Dr. Cale took a breath. “The ‘sleeping sickness’ that you’re here to discuss with me is not a virus.”

“We know,” said Nathan.

Dr. Cale actually looked surprised at that. “You do?” she asked. “How?”

“After Sal and I left SymboGen, she told me about the way they’d been examining the people who’d come in contact with someone—”

“With Chave,” I interrupted. I was surprised by the sharpness of my own tone. “Her name was—her name is—Chave.”

“You were right the first time,” said Dr. Cale gently. “If your friend has the sleeping sickness, she’s not there anymore. I knew you’d been there when someone took sick. That was what my operative was able to tell me before he dropped out of contact. I didn’t realize she was someone you knew.”

I didn’t say anything. I just stared at her, one more piece of the puzzle slotting into place in my head with inescapable finality.

Nathan didn’t seem to notice my sudden stillness. He continued, saying, “Chave. When I picked up Sal, she told me how SymboGen examined all the people who might have come into contact with Chave after she got sick. They ran a wand over the surface of Sal’s skin. I assumed it had to be a UV light wand, and so I took Sal to the hospital and repeated the process. The people we have in our isolation ward—the ones who won’t wake up—all show the unmistakable signs of a subcutaneous parasitic infection. I just don’t know what it is.”