The San Francisco branch of USAMRIID—the United States of America Medical Research Institute for Infectious Diseases—was constructed in what used to be the Treasure Island military base, before changes in personnel and deployment caused the base’s original purpose to become outmoded. It sat empty for several years, before the property was repurposed to allow the military to keep an eye on the growing California biotech and medical research fields.

I knew the history of the facility because I lived with my father and Joyce, both of whom were more than happy to talk about where they worked, if not what they did every day. I knew the word “outmoded” because of Sherman, who had chosen it as our word of the day over a year before.

My cautiously optimistic mood deflated, leaving me feeling hollow, without even the comforting sound of drums to buoy me up. No matter what we did, no matter what I learned or what I was able to share with my father’s lab, Sherman was still going to be dead. He was never going to teach me another vocabulary word, or threaten to seduce my boyfriend away from me. Sherman was gone.

In that moment, I hated SymboGen, I hated D. symbogenesis, and most of all, I hated Dr. Shanti Cale, for making it possible for the rest of it to happen in the first place. I hated them for ruining everything, and for hurting so many of the people I cared about. They were the ones who opened the broken doors, not us. But we were the ones who were paying for their actions.

My father pulled up at the gate, where sturdy-looking guard stations loomed on either side of the car. A young man in army green was seated in the driver’s side booth, a clipboard in his hands. My father rolled down his window. The young man rose, and saluted.

“Colonel Mitchell,” he said.

“At ease, soldier.” My father indicated me. “This is my daughter, Sally Mitchell. She’s on the approved visitor’s list. I need a pass for her.”

“Yes, sir.” The young man gestured to the uniformed woman in the other guard booth. The window rolled down as she approached my door. I hate it when drivers do that. It just reminds me of how little control I have.

“Ma’am,” she said.

“Hello,” I said.

“Please look at the blue dot.” The woman indicated a blue dot at the center of a smooth black metal box mounted on the guard station wall. I looked at it, bemused. The woman typed something on a keyboard. “Her pass will be waiting when you get inside.”

“Thank you,” said my father, and drove onward to the barrier, which rose as we approached it.

I sat back in my seat, blinking. “What just happened?”

“Don’t worry about it.”

“Dad—”

“We’re here.”

The San Francisco USAMRIID installation consisted of four main buildings, connected by stone walkways, and the boxy shape of the Level 4 lab, which was isolated from the rest of the facility by more than twenty yards. Collapsible tunnels connected it to the administration building. They could be sterilized and removed in less than ninety seconds, leaving the L4 lab completely cut off. The doors would lock automatically at the same time. Anyone left inside would find themselves depending on the vending machines and their own ability not to die from unspeakable pathogens until someone came up with an extraction plan.

Naturally, that was where my sister worked, and naturally, that was our destination. Dad parked the car just outside the lab’s main entrance, in the spot marked DIRECTOR. Similar spaces were reserved outside all the lab buildings, since there was no telling where he’d need to be at any given time.

“Now, remember,” he cautioned, as we got out of the car. “Don’t touch anything unless I tell you it’s safe, and don’t—”

“If you tell me not to lick anything, I’m going to throw something at you,” I cautioned. Not Don’t Go Out Alone—I couldn’t justify leaving it at home, but I wasn’t taking it inside, either. The book was in my shoulder bag, which was safely tucked under my seat, along with my notebook. Hopefully, no one was going to notice it there. It felt a little odd to be worrying about an old picture book and a bunch of half-coherent dreams. Then again, everything felt a little odd these days.

Dad looked abashed. “I’m sorry,” he said. “It’s just that you haven’t been trained the way Joyce has, and I worry about you.”

I smiled wanly. “It’s okay. Let’s just go inside, and I’ll show you what I can.”

He nodded. “All right. But Sal… we’re going into a live research project. The L4 building is almost entirely dedicated to the sleepwalkers right now. You must follow my instructions at all times. Do you understand?”

“I do,” I said. “Let’s go.”

Dad nodded one more time before turning and leading me out of the parking lot, toward the unmarked but somehow menacing door of the Level 4 lab. I took a deep breath and followed him, with the oddly comforting sound of drums hammering in my ears. Whatever was behind that door, it would be something I didn’t know yet, and every piece of this puzzle counted.

Guards flanked the door. They saluted my father as he approached. He returned the salute almost absentmindedly, and turned to shield the keypad with his body as he entered his security code. The lock disengaged, and he pulled the door open, beckoning me inside.

“Be careful now,” I murmured, and stepped through.

The fact that the scientific community has willingly accepted Steve’s sanitized explanation for the origins of D. symbogenesis strikes me as a form of modern miracle—or perhaps it’s just proof that we inevitably get the saviors we deserve. In an earlier era, Steve would have been a traveling snake oil salesman, offering people cures too good to be true. Today, he peddles a new form of snake oil, one that can be just as dangerous, and just as destructive.