Sarah chewed a bite of burger thoughtfully, then swallowed. “Well, first this total dickhead gave me a disease.”

“Oh, yeah.” I drank some coffee, frowned at its bitterness. “I never had a chance to say sorry about that. I didn’t know—”

“Yeah, yeah. I guess we’re both to blame. Safe sex, blah, blah, blah.” Sarah sighed. “Then there was my little … breakdown. But you saw most of that.”

I nodded. “Until you disappeared.”

Sarah took a long breath, staring out the window. “Well, the parts you missed out on are kind of hazy for me, too. Sort of like a long, bad dream. About being hungry.” She shuddered. “And eating. Then there you were again, rescuing me.” She smiled tiredly then took another bite.

“Rescuing you?” I swallowed, never having thought of it that way myself. “It was the least I could do. But, Sarah, how did you get so normal? So fast?”

“Good question, which reminds me.” She pulled out a bottle of pills, dumped two into her palm, and swallowed. “Two with every meal.”

I blinked. “There’s a cure?”

“Sure. They had me straightened out about six hours after I got to Montana.”

“When did that happen? The cure, I mean.”

“At least seven hundred years ago.”

There it was again, that seven-hundred-year thing. “The plague? This doesn’t make any sense, Sarah.”

“It will, Cal. Just listen up. I’m here to tell you everything. Doctor’s orders.” She bit deep into her burger, hurrying now that she was only a few swallows from the end.

“Which doctor? Prolix?”

“Yep, the Shrink. She’s been telling me all about what’s coming.” Sarah looked out at the crowds on the sidewalk. “They figured I could take it, because of my personal eating habits lately.” She looked down at her hamburger with momentary suspicion, then took another bite. “And because they don’t have time to mess with me. Or with you, anymore. Time to face facts, Cal.”

Suddenly, the restaurant felt overcrowded, claustrophobic. I could smell the people in the booth behind me, the pressure of the passersby on the street. “The disease is out of control, isn’t it? We’re going to wake up one day in one of those zombie-apocalypse movies, the parasite spreading faster than anyone can stop it.”

“No, Cal. Don’t be silly. The disease is in control, the way it should be. The parasite’s calling the shots now.”

“It’s doing what?”

“It’s in charge, making things happen. The way it’s supposed to. The Night Watch was always just a holding pattern, keeping down the mutation while waiting for the old strain to come back.”

I shook my head. “Wait. What?”

Sarah held up her fork and knife, looking from one to the other. “Okay. There’s two versions of the parasite. The new kind and the old kind. Right?”

“Two strains, I know.” I nodded. “And we’ve got the new one, you and me.”

Sarah sighed. “No, dickhead, we have the old kind. The original.” She rattled her pill bottle. “This is mandrake and garlic, mostly. Totally old-school. Until seven hundred years ago, people used to totally control this disease.”

“Until the plague?”

“Bingo. That’s when the new strain showed up.” Sarah shook her head. “You’ve got to blame the Inquisition for that. You know, when Christians got it into their heads that cats were evil and started killing loads of them? That was bad for the old version of the parasite, seeing as how it jumps back and forth between felines and humans.”

“Right… I know about that. But that’s the old version?”

“Yes. Pay attention, Cal. As I was saying, it’s 1300 a.d. and everyone’s killing cats. So with hardly any cats around, the rat population grows like crazy. More human-to-rat contact, evolution of various diseases, fleas and ticks, blah, blah, blah.” She waved her hand. “Plague.”

“Um, I think you’re skipping over something there.”

She snorted. “I’m not the one going for a biology degree. I’m just a philosophy major who eats people. But here’s the bio-for-philosophers version: A new strain of the parasite appeared, one that moved back and forth between rats and humans, without cats. Of course, as with any new strain, the optimum virulence was a mess; the peeps were much more violent and difficult to control. A total zombie movie, like you said.”

“And the old strain went underground.”

“Very good.” Sarah smiled. “They told me you’d understand.”

“But that was Europe. This is New York.”

“Rats go everywhere, Cal. They love ships, so of course the new parasites made it to the New World. Even here, the old strain was pushed down into the deep.”

“But now it’s coming back up,” I said. “Why aren’t we doing something about it? Why are the old carriers hiding it from the rest of the Watch?”

“Excellent questions.” She nodded slowly, chewing the last bite of her hamburger. “That’s what you scientists never seem to understand: The whys are always more important than the hows.”

“Sarah, just tell me!”

“Okay.” She placed her palms on the table. “Feel that?”

I looked at the surface of my coffee; its black mirror reflected the lights overhead with a pulsing shimmer. “You mean the subway going by?”

She shook her head, her eyes closed. “Feel deeper.”

I placed my hands on the table, and as the train faded, I felt another, more subtle shudder in its wake. Like something disturbed in its sleep, turning over. Like the trembling I’d felt through my cowboy boots, the first time I’d seen the peep cat.

Sarah opened her eyes. “Our strain is coming up because it’s being pushed up.”

I remembered the unseen thing I’d smelled in the Underworld, and the shudder in my hands took over my whole body for a moment. “By what?”

Sarah lifted her palms from the table, sighed, then shrugged. “There are a lot of things down there, Cal, things human beings haven’t seen in a long time. We lost a lot of knowledge during the plague. But the old guys do know one thing: When the ground starts to tremble, the old strain will rise up. They need us.”

“Wait a second. Who needs who?”

“They”—she looked out the window at the passing crowds—“need us. We’re the immune system for our species, Cal. Like those kick-ass T-cells and B-cells you always told me about, we get activated by an invasion. New-strainers are just zombies, vampires. But those of us with the old disease, the carrier strain, we’re soldiers.”

My mind spun, trying to reconcile what Sarah was saying with what I’d seen Morgan doing, spreading the disease haphazardly, enlisting hordes of cats. “But why is this a secret? I mean, why didn’t this come up in my Night Watch courses? Does Dr. Rat know about it? Or Records?”

“It’s older than Records. Older than science. Even older than New York. So the carriers kept it a secret from the Night Watch humans, Cal. It’s not going to be pleasant for them, the next few months. But we need all the soldiers we can get. Fast.”

“So you’re spreading the disease on purpose?” I asked, but Sarah’s eyes had left mine, looking over my right shoulder, a pleasant smile filling her face.

A hand fell on me. “Uh, hey, Cal. Sorry I’m late.”

I looked up. Lace was staring down at Sarah, a little unsure.

“Oh, hi.” I cleared my throat, realizing I’d waited too long; the inevitable collision had happened. “This is Sarah. My ex.”

“And you must be Lacey.” Sarah extended her hand.

“Uh, yeah. Lace, actually.” They shook.

“Hot stuff, coming through!” said Rebecky, sliding a plate of pepper steak in front of me. Lace sat down next to me, wary of the woman across from her. Rebecky’s gaze moved among us, intrigued by the obvious discomfort of it all.

“Coffee, honey?” she asked Lace.

“Yeah, please.”

“Me too,” I said.

“Me three,” Sarah added. “And another hamburger.”

“And one of those.” Lace pointed at my pepper steak. “I’m starving.”