“No shit,” I said as I moved to the couch and dropped down onto it. “But, um, I need to talk to you about…” I fumbled for some euphemism I could use for zombie stuff and failed. “About pudding,” I finally blurted, then mentally cringed. Pudding? That was the best I could do?

A smile twitched across Marcus’s face. “It’s all right, Angel. Sofia knows we’re zombies.”

“Oh.” A weird ache of disappointment swam through me. This was the one thing that I shared with Marcus that I’d figured someone like Sofia couldn’t, since she wasn’t one of us. And yet…she did share it—and clearly accepted Marcus just fine as a zombie. What does that leave for me?

I did my best to swallow back the ache and put on a nonchalant smile. “Okay, well, that makes things easier,” I said. “I just found out that the guy who died at your lab really was a zombie.” I shot Marcus a quick I told you so! look.

Sofia let out a small gasp. “Are you certain?”

“Then how could he have appeared so dead?” Marcus asked, frowning. “Angel, how can you be so sure?”

I perched on the edge of the sofa. “Because the weirdness isn’t just that he was a zombie. It’s that this was one of the zombies that Ed killed.”

He blinked. “That doesn’t make sense. What do you mean?”

I quickly told them about the fingerprint on the watch and getting the ID, as well as the comparison of pictures and the matching scar and mole. Marcus still looked dubious, but Sofia clenched her hands together and hunched her shoulders.

“This explains so much,” she said, voice unsteady. “He must have been after my research.” She lifted her eyes to Marcus. “Pietro needs to know this. I know someone’s been looking through my files. Somehow one of the other zombie factions found out. I…I need protection.”

He moved to her side. “We’ll keep you safe, Sofia. Don’t worry.”

I frowned and held up a hand. “Hang on a sec. Could someone please explain to me what the hell is going on? What research? What ‘zombie factions’?”

Sofia took a deep breath and straightened. “I’ve known about the zombies for several years, since shortly after Marcus was turned. Pietro came to me with the offer to fund research in the hopes that I could either find a cure for it or find a way to manufacture a food substitute that would remove the need to consume human brains.”

“Is there a cure?” I asked, though I immediately wondered if I’d want it. As weird and gross as the whole zombie thing was, there were definitely some advantages.

She gave a sad shake of her head. “There’s no way to remove the parasite without killing the host.”

“Wait,” I said. “It’s not some sort of virus?”

“No, and I’ll explain why,” she said, her face abruptly growing more animated. Clearly this was a subject that excited her. “You see, viruses infect to reproduce, whereas parasites infect to get a home, freeload, and live out their lives. For the zombies that you see in the movies, yes, a virus makes sense, because they’re mindlessly going around trying to bite more people to propagate the infection. But with you—the real zombies—the goal seems to be the host’s survival, and it’s pretty much hijacked your entire body to make sure of it.”

“Okay,” I said weakly. Then I grimaced. “No, wait. I’m still confused. A parasite…like tapeworms? How is that different from a virus?”

She grinned but it wasn’t amusement at my ignorance. This was obviously her turf and a topic she relished. “Here’s the thing,” she said. “Parasites and viruses share some basic traits—they both need to infect a host and use its resources to survive and reproduce, but their global outlook is very different. A virus’s business model is based around hijacking your cellular machinery and completely depleting any and all resources it can get its grubby hands on, until the host is either dead or its immune system manages to kick the infecting virus out.” She paused, tilted her head. “Or into hibernation. A lot of viral infections are actually permanent; our immune system just gets used to them and forces them into retirement or hibernation, like chicken pox, herpes, warts, and hepatitis.”

I shuddered. “Seriously? I had chicken pox when I was a kid. You’re saying I still have it?”

She chuckled. “Actually probably not anymore, now that you’re a zombie. But I’ll explain why that is in a second.”

“Don’t feel bad, Angel,” Marcus said. “I’ve been through the same Zombie 101 class. Luckily, Sofia does a great job of making it understandable.”

“If you say so,” I said, trying not to sound too doubtful.

Sofia didn’t seem to notice. “First let me explain viruses,” she continued. “Success, to a virus, is making a gazillion infectious copies of itself and making its host as infectious as possible, whatever the cost. Absolutely nowhere in this business model is there any accountability or design to save the host resource. It banks on having an inexhaustible supply of hosts available to infect. Keeping the host alive and happy just isn’t in the sales pitch.” She paused. “I like to compare a virus to a bad company that sets up shop in a third world country to make, say, shoes. After the third world country is raped of every resource the company can get its grubby hands on to build the factories and shoes, the people are starving, and the land has been strip-mined, the company at no point goes, ‘Hmmm, maybe we should fix this.’ Instead it pats itself on the back for selling lots and lots of shoes, packs up, and sets up shop all over again in a brand new third world country. This exploitive business assumes there will always be an inexhaustible supply of new countries to inhabit and strip-mine.”

I mulled that for a few seconds, shocked to find that I actually understood what she was saying. “Right. And we’re not like that. We don’t try and infect everyone we come in contact with.”

“Exactly!” she said, bringing her hands together. “But there’s even more to it than that. Your form of zombieism actually benefits you in many ways.”

“Like the healing up and super-strength and stuff?” I asked.

She gave a nod. “It would be a lot of evolutionary leg work and a lot of extra genetic programming to turn a virus into something that would consistently benefit its host. Each change in behavior would mean a genetic change…but here’s the thing: Because viruses use the host’s resources—machinery and energy, they don’t actively select against mutation. This is because there is no loss to the virus in letting itself just mutate; it’s only wasting its hosts’ resources, not its own. So, although useful mutations are selected for, the bad mutations aren’t necessarily selected against.”

I could feel my eyes beginning to glaze over. “And this means…?”

Sofia smiled. “It means that there’s pretty much no way a virus could do what your zombieism does.”

“And a parasite could?”

“Right!” She gave me a probing look. “Are you ready for phase two of my lecture?”

“Sure, why not,” I said, settling into a more comfortable position on the couch. “Maybe some of this shit will be on the GED.”

“Somehow I doubt that!” she said with a wry grin. “All right then: a parasite needs the host to live long enough for it to successfully complete its life cycle; grow, reproduce, et cetera. Parasites use the host more like an environment, rather than a stopover factory. A parasite needs to inhabit and use its hosts’ resources, but,” she paused, “and here is the big ‘but’: It needs the host to survive. If the parasite manages to kill the host before it—the parasite—completes its life cycle, it fails. After its life cycle is over, it can kill the host all it wants, but not before.”

“Like…tapeworms?” I asked again.

“Better. See, it’s pretty clear to me that this parasite has a long life cycle. Longer than a human’s, which is why it’s in its best interest to regenerate the host.” She held up a hand. “But, of course, not at the risk of its own well being. We’re talking about a parasite here, after all, not a charity.”

I sat up straight. “Oh! I get it! It heals us up when it has the brains, and it lets us rot when it doesn’t.”

She clapped her hands. “Yes! Regeneration when there is food available, and sacrificing the host—the rotting—when it’s hungry.”

“That’s so cool,” I breathed. “And disgusting.”

Marcus laughed. “All right, Sofia. Now tell her about the mold.”

I shot him a frown. “Mold?”

Sofia let out an exasperated sigh. “Not mold—fungus.” She looked back at me. “And here is where I will explain how it’s not like tapeworms, where a dose of the right kind of meds would clear it right up.”

“Go for it,” I said lacing my fingers behind my head.

She launched herself to her feet and began an excited pacing. “Well, the first thing I looked at was how a new zombie is made.” She glanced up at Marcus. “Marcus and Pietro were able to give me a fair amount of information about the process, and it’s clearly not spreadable through a casual bite.”

“It, um, takes a bit of mauling,” Marcus said. He didn’t look at me, which was a relief for me. I didn’t want to think about the fact that he’d obviously had to do that to me to make me a zombie.

“Right,” Sofia said. “It takes a bit of doing to get the parasite to spin off an infecting spore and get it into the bloodstream of the new host, which is why it can’t be transferred via a simple blood transfusion or organ donation.” She looked at me with a slight frown. “Are you sure you want to hear the rest? It might be a bit unsettling to hear what happens when the parasite sets up shop.”

At this point I wasn’t at all sure I wanted to hear the rest, but I sure as hell didn’t want to look weak in front of this woman. I felt inadequate enough, thank you very much. “I’m cool,” I said with a smile I didn’t feel. “Lay it on me.”