Farther down the row of patients, we hear a shout. “We’ve had a rupture!” a medic calls. “I think he’s bleeding internally.”

I call out over the miniport for a surgic. We all gather around the patient, who has gone pale. The vital-stats machine screams at us as the patient’s blood pressure drops and his heart rate speeds up. The medics and surgics yell out instructions.

This patient, and all the rest, lie completely still.

We can’t save him. We don’t even have time to get him to a surgical room before he dies. I glance around at the patients nearby. I hope they haven’t seen too much. What can they see? The weight of the patient’s death settles over me as I pick up my miniport, which beeps insistently with a private message from the head physic. He’s watched the whole thing from the main port.

Sending patient data now. Review immediately.

He wants me to look at data now? When we’ve just had a death? The entire team looks rattled. The point of the medical center, and the Rising, is that we save people. We don’t lose them like this.

I walk over to the side of the room to check the data. At first I don’t understand the urgency. It’s data from the patients who’ve come in sick, and the information looks like basic medical workups. I’m not sure what it’s supposed to tell me.

Then I get it. The workups are all recent, from when the patients were immunized. The patients were immunized, and they still got the mutation, which means a huge segment of the population is at risk.

“I’m going to have to lock down your wing completely,” the head physic says from the miniport.

“I understand,” I tell him. There’s nothing else they can do. “We’re going into lockdown,” I tell the team.

They nod, exhausted. They understand. We’ve all been through this in drills a million times. We’re here to save people.

Then I hear footsteps behind me, running. I spin around.

The virologist is heading for the main doors to the wing. Have they had time to lock it down yet? Or is he going to expose an entire new cluster of people to the mutated plague?

I take off, running back down the rows of patients, as fast as I can. He’s older than me. It’s short work to catch up and I tackle him, throwing us both to the ground. “You don’t run,” I say, not bothering to keep the disgust out of my voice. “You stay to help when people are sick. That’s part of your job.”

“Listen,” he says, struggling to sit up. I let him but I hold on to his arm. “We may not be safe from this mutation. Our immunizations may mean nothing.”

“That’s exactly why you can’t risk exposing anyone else,” I say. “You know that better than anyone.” I haul him up by the back of his uniform and walk him toward one of the wing’s storage closets. I don’t want to lock him up, but I’m not sure how else to deal with him right now.

“Unless,” the virologist says, sounding either crazy or inspired, “the people with scars are safe. The small scars.”

I know what he means. “The people who had the first round of the Plague,” I say. The Rising told us to look for the marks, and Lei and I talked about them—those small red scars between their shoulder blades.

“Yes,” he says eagerly. “They could have had a slightly mutated version of the earlier virus, and their variant is close enough to the mutant form that they’re not getting it. But the immunization you and I were given—it was just chopped-up pieces of the original virus. It won’t be close enough to this new mutant form to protect us.”

I keep hold of him but nod to show that I’m listening.

“We didn’t go down with the earlier version of the Plague,” he says. “But we were still exposed. Our initial immunity protected us from the worst symptoms, but we could still contract that earlier version of the Plague. That’s how an immunization works. It teaches your body how to react to a virus so your system recognizes the virus when it comes again. It’s not that you don’t get sick at all. But your body knows how to handle it.”

“I know,” I say. I’ve figured out this much already.

“Listen to what I’m telling you,” the virologist says. “If that happened, if we actually contracted the first version of the Plague, the one going around when the Pilot first spoke—then we have the red mark, too, and we’re safe. We didn’t go down, but we still had the virus. Our bodies just dealt with it. But if we didn’t catch the earlier virus during that window”—he spreads out his hands—“we can still get the mutation. And we may not have a cure that works for this version.”

For a minute he sounds crazy, like he’s speaking gibberish, and then it all comes together and I think he might be right.

He twists his arm free from my grasp and starts unbuttoning the top of his plainclothes. Then he pulls down the collar of his black uniform. “Look,” he says. “I don’t have the small mark. Do I?”

He doesn’t.

“No,” I say. I resist the urge to pull down my own collar and try to see if the mark is there. I’ve never thought to look for it on myself. “You’re needed here. And if you go out there, you could infect other people. You’ve been exposed to the mutation already, like the rest of us.”

“I’ll go out into the woods. People in the Borders have always known how to survive. There are places I can go.”

“Like where?” I ask.

“Like the stone villages,” he says.

I raise my eyebrows. Is he confused? I don’t know what those places are. I’ve never heard of them before. “And do they have fluid and nutrient bags there?” I ask. “Do they have what you need to stay alive until there’s a cure? And don’t you care about exposing them to illness?”

He stares up at me with wild-eyed panic. “Didn’t you see him?” he asks. “That patient? He died. I can’t stay here.”

“Was that the first time you’ve seen anyone die in real life?” I ask.

“People didn’t die in the Society,” he says.

“They did,” I say. “They were just better at hiding it.” And I understand why the virologist is afraid. I think about running away too, but only for a second.

The head physic decides to relax the lockdown long enough to send us more patients and more personnel. He’s heard everything the virologist told me over the miniport, so he’ll decide how to report it all to the Pilot. I’m glad that’s not my job.

But I do have one request for the head physic. “When you send in the new personnel,” I say, “make sure they know this new form of the virus hasn’t responded yet to the cure. We don’t need anyone else trying to run. We want them to know what they’re getting into.”

It’s not long before several Rising officers, armed and wearing hazmat suits, escort the new personnel to our wing. The officers take the virologist away with them. I’m not sure where they’ll quarantine him—in an empty room on his own, perhaps—but he’s become a liability, and we can’t keep him here when he’s so volatile. I’m so focused on making sure he’s taken care of that it takes me a moment to realize that one of the new staff is Lei.

As soon as I can, I find her in the courtyard. “You shouldn’t be here,” I tell her quietly. “We can’t guarantee that it’s safe.”

“I know,” she says. “They told me. They’re not sure the cure works on the mutation.”

“It’s more than that,” I say. “Remember when you and I were talking about the small red mark on the people who had the earlier virus?”

“Yes.”

“The virologist they took out had a theory about that.”

“What was it?”

“He thought that if someone had the red mark, it meant they’d had the virus, like we thought—and he also thought that it meant that they were protected from the new mutation.”

“How could that be?” Lei asks.

“The virus changes,” I say. “Like those fish you were talking about. It was one thing, now it’s different.”

She shakes her head.

I try again. “People who had the immunizations had been exposed to one form of the virus, a dead one. Then the first round of the Plague came along. Some of us might have contracted the virus, but we didn’t get really sick because we’d already been exposed to it in its weakened form. The immunization did its job and our bodies fought off the illness. Still, we had exposure to the live virus itself, which means we might be safe from this mutation. The dead virus wasn’t close enough to the mutation to protect us, but our exposure to the original live version of the Plague might be, as long as we actually contracted it.”

“I still don’t understand,” she says.

I try again. “According to his theory, those who have the red mark are lucky,” I say. “They’ve been exposed to the right versions of the virus at the right times. And that means they’re safe from this mutation.”

“Like stones in the river,” she says, understanding crossing her face. “Going across. You need to step on them in the right order to get safely to the other side.”

“I guess so,” I say. “Or like the fish you were talking about. They change.”

“No,” she says, “The fish remain themselves. They adapt; they look completely different, but they’re not fundamentally altered or gone.”

“All right,” I say, though now I’m the one who’s confused.

She can tell. “I suppose,” she says, “that you have to see them.”

“Do you have the mark?” I ask Lei.

“I don’t know,” she says. “Do you?”

I shake my head. “I’m not sure either,” I say. “It’s not exactly in an easy place to see.”

“I’ll look for you,” she tells me, and before I can say anything else, she steps around behind me, slides her finger under my collar, and pulls it down. I feel her breath on my neck.

“If the virologist is right, then you’re safe,” she says, and I can hear the smile in her voice. “You have the mark.”

“Are you sure?” I ask.

“Yes,” she says. “I am. It’s right there.” After she takes her hand away I can still feel the spot where her finger pressed against my skin.

She knows what I’m about to ask.

“No,” she says. “Don’t look. I don’t want it to change what I do.”

Later, as we leave the courtyard, Lei stops and looks at me. As she does, I realize that not very many people have eyes that are the color of hers: true black. “I changed my mind,” she says.

At first I’m not sure what she means but then she sweeps her long hair to the side and says, “I think I want to know.” There’s a faint tremor in her voice.

The mark. She wants to know if she has it.

“All right,” I say, and suddenly I feel awkward. Which is ridiculous, because I’ve looked at plenty of bodies that are just bodies. I know they’re people, and I want to help them, but to some extent they’re anonymous all the same.