The Devil's Only Friend by Dan Wells

hours without moving. The fact that he had claimed Potash’s bed gave me a petty sense of satisfaction, and I turned my attention to Mary Gardner.
    I pored through my own notes, assembled over weeks of part-time volunteer work on Mary’s floor of the hospital. She lived under the human guise of a nurse, forty-six years old, competent and caring and boundlessly sympathetic to the parents of those children who died in her care. She was very careful about her kills—we had to give her that. If not for Brooke’s assurance, we would never have suspected that the children under Mary’s care had died from anything other than the diseases they were already being treated for. Many of her victims, we suspected, weren’t under her direct care at all, though we’d been observing the hospital long enough to tie her, at least superficially, to the approximate time and place of most of the deaths on three floors of the building. If she were human, we’d have enough evidence to at least get her fired, but we couldn’t afford that with a Withered. Drive her away and she’d just start killing somewhere else, and we didn’t have the time or the resources to follow her all over the world. We had to kill her here, once and for all, and the sooner we could manage it, the fewer children she’d take with her on the way out. Our own danger from Meshara was a secondary concern for now, though as Trujillo had pointed out, every dead Withered made us that much safer.
    The one thing we hadn’t figured out was the actual mechanism of Mary’s kills; she seemed to gain some kind of healing boost from the process, as her cycles of health and illness seemed to follow the deaths fairly clearly, but she was never around when the victims died. My best guess at this point was a delayed reaction: she’d slip into a sick child’s room, “take” something from them—hell if I knew what it was, energy or something—and then her health would improve, and then the child would die, sometimes hours later, sometimes a day or more.
    Ostler and the others insisted that Mary’s killing of children made her more evil than the others, more heinous and irredeemable. I figured a victim was a victim; she didn’t target children out of generic evilness, but because something about her process required it. Finding out what that something was could be the key to the whole mystery.
    I needed someone to talk to, to bounce ideas off of. Kelly was good for this, and sometimes Trujillo, though he talked back too much to be of any real use as a sounding board. Either way, they were both working on their own branches of the project tonight, and I had to make do without them. In the old days I’d had Max, and then I’d used Marci, but I supposed I’d be paying for that mistake for the rest of my life. I couldn’t use just anyone … and I guessed, at the moment, I couldn’t use anyone at all.
    I haven’t told you about Marci yet, though I’ve mentioned her a couple of times. She’s not exactly easy to talk about. Sociopathy is a tricky disease to describe—it’s not an absence of emotion, but an absence of empathy. You look at another human being, or even an animal, and feel no connection whatsoever: you don’t feel good when they’re happy, you don’t feel bad when they get hurt, you’re completely cut off. Maybe you feel jealous when they get something you want, but that’s not a connection to them—that’s all focused on yourself. What you want and what you’re willing to do to get it. And if that means hurting someone, well, you don’t care. Your needs are more important than anyone else’s, because you’re more important than anyone else. Nobody else counts.
    Marci was different.
    And now Marci was dead.
    I looked around at my room, almost as if I expected to see her there, pale and half formed, like a shadow in reverse. I don’t know what a ghost looks like, or if ghosts are even real—the Withered are, so who knows what else is