A/N So I've had this idea for ages, and finally decided to make it into an actual story a few weeks ago. Though the idea suits a full-length fic better, I had to make this into a 3-shot if I wanted to accommodate it into my schedule, meaning that it's a bit rushed. I think the pace evens out more in the next two chapters (which are indeed finished and waiting to be published), though, so that's something. It was a bit of a challenge for my shipper's mind to not romantically pair Sherlock and John in this, but there's a little bit of implied crap in the final segment, I think. Anyhow, I'll stop talking about the future chapters before they're even published. :P Please review!

Rated T for violence and language

Disclaimer I don't own Sherlock/Supernatural or any associated characters, events, etc.

I

Would you mind if I hurt you?
Understand that I need to
Wish that I had other choices
Than to harm the one I love
~ "What Have You Done," Within Temptation

"You're wrong," Sherlock hisses in frustration, running a thin-fingered hand through his dark, silky curls and whirling around. His sleeves are rolled up, exposing the pale skin of his forearms, and his silver-green eyes burning with frustration. "You're wrong, how difficult is that to comprehend? It's like your belief in that wretched—that ridiculous—" He doesn't say God's name aloud, but instead braces his hands against the dusty surface of the table in the center of our flat's living room, breathing heavily and glaring at the wood. "It's the same thing, this blind faith in something that never has helped you, that never will help you, that you only follow because it feels right." The last two words are spat out, and I can actually see saliva fly from his lips as he turns to face me once more.

I watch him evenly, trying my best to stay calm despite the fact that I'm more than a little alarmed. I've never seen him like this before, in such an absolute rage. And one seemingly without a source, too—it's not like we haven't debated morality before, like we don't constantly bicker over what's right and what's wrong, whether the fate of the murderer or the victim in a particularly complex case is more important. Perhaps it's the fact that he hasn't eaten for several days that's causing him to get so worked up now, but in any case, I make sure to be very cautious as I begin to speak again.

"All I'm trying to say is—"

"I don't care what you're trying to say!" he bellows, his facial muscles seeming to tighten, and then the air in my lungs vanishes as his eyes change. At first, I think that they've simply caught the light oddly, but there's no denying the sight before me. It's like his pupils are expanding, filling the iris and sclera, so that I'm staring into twin pools of liquid obsidian, jet-black and framed by his light lashes. I find myself stumbling backwards in shock, half-crashing into the sofa, and by the time I right myself, the bizarre sight has erased itself. He appears entirely normal—if fuming—once more, but there's no denying the sudden chills that won't stop running down my spine.

What the hell was that?

He stands with his chest heaving against his too-tight cream-colored shirt, as if waiting for me to make a move. I shake my head numbly, the image of his darkened eyes still burned into my head, and edge towards the door. I have no idea where I intend to go—all I know is that I can't stay here, can't keep arguing him now that I have the full impact of the bizarre vision affecting me. I can't comprehend what the hell it was, and I need space to myself, to figure out if my brain is just seeing things from too little sleep or something's seriously wrong with him. "I'm going out," I declare, grabbing my coat and hoping that my tone can be mistaken for one of fury rather than terror.

Sherlock doesn't make a move to stop me, and a relieved sigh escapes my lips as I half-run down the stairs, not stopping to consider what I'm doing until I'm out the door, greeted by a spray of light rain from the pale grey sky. Finally stopping as I scan the street for cabs, I slip my arms into the sleeves of the jacket, pulling the zipper up tight and trying to regulate my breathing. Maybe I'm overreacting... but, no, I'm a doctor, and I know that there isn't a single reasonable explanation for someone's eyeballs to suddenly go jet-black. And it wasn't a simple flash of darkness, either. The way that the shade had spread from the center, like ink in water... I shiver again, finally catching sight of a taxi and hurriedly waving it towards the curb.

"Where to?" the driver asks gruffly as I slide into the backseat, greeted by warmth and dryness. I slam the door tight shut behind me and keep my gaze fixated on the door of Baker Street, half-expecting Sherlock to emerge from it.

"Uh... St. Bart's," I invent, naming the first location that springs to mind. As he grunts and the cab begins to move, I relax ever so slightly against the seat, the hammering of my heart beginning to die down in my ears. It's a good idea—maybe I can even catch Molly there, ask her if she has any idea what color-changing eyes could possibly indicate. I can imagine how stupid I'll look—Hey, Molly, sorry to interrupt, but do you have any idea what could cause Sherlock's eyes to go completely black for no apparent reason?—but the acid fear in my chest is enough to stop me from asking the cabbie to turn around. I'm chilled, chilled to the bone, and my knuckles are white where they're clenched into fists on my lap. What if there is something really wrong with Sherlock? What if it's some rare, bizarre disease… something that only makes an appearance when he's angry? That's the only thing I can connect it with. After all, this fit of fury was unlike anything I've ever seen from him before. I've gotten him frustrated plenty of times, but he's usually kept his cool, tension running under a surface of ice.

This time, though…

He had exploded.

The basis of the argument itself seems foggy, as I try to recall it. Nothing special, best I can remember, just yet another feud concerning his lack of caring about people. Needless to say, I'm regretting ever bringing it up now, seeing as it caused such an alarming reaction in him.

Or maybe the obsidian eyes have nothing to do with anger at all, and it was just something odd… or even a strange flicker of the light, as I force myself to acknowledge. There's no reason to be so sure that I even saw anything meaningful at all.

The taxi rolls to a halt, and I hand a few pound notes up to the driver without thinking, not even bothering to count out the exact price or ask for change as I step out onto the rain-splattered sidewalk. The wind is picking up, and I quicken my pace as I head inside the hospital building, wincing at the sudden chill of unnecessary air conditioning as the door shuts behind me. I immediately start down the familiar path to Molly's office, my shoes leaving wet footprints on the clean floor. A janitor mopping up a corner of the hall shoots me an annoyed glanced, but I really can't bring myself to feel apologetic just now—I have more important things on my mind, much more important things. I have to hope that Molly isn't on some sort of break—it would be rather awkward to burst in on another pathologist—and even if I do catch her on time, it will hardly be an easy, casual exchange.

When the door comes into sight, I push it open immediately, stepping in and not giving myself an opportunity to second-guess my actions. To my relief, Molly is indeed standing there, bent over a particularly gruesome body—the victim looks like it was torn up by rabid dogs or something of the like. Averting my eyes and swallowing my disgust, I close the door behind me just as she looks up, her wide brown gaze looking rather surprised.

"John? Oh… hello, I wasn't expecting—does Sherlock need something?" She hastily strips off her gore-encrusted rubber gloves and drops them on the metal table next to her before straightening up, her head tilted slightly in curiosity.

"No, actually, I…" I try to shake off my slight irritation at the fact that she immediately assumes my visit has something to do with his wishes—I'm not just Sherlock's servant—but I suppose it is logical. It's not that I have any connection to Molly, myself. "It's… he's been acting a bit oddly… just today, I was wondering if you might have any idea what's going on."

"How oddly?" she questions, voice and face anxious. "Is he alright?"

"I… don't know," I answer honestly.

"Tell me what's wrong. Please."

"At first it was just his temper," I begin carefully, trying to think of a way to phrase the bizarre occurrence so that I don't sound entirely insane. "He was lashing out more than usual… I thought it was hunger or exhaustion, you know? He does have those times where he won't eat or sleep… but then…" I take a deep breath, knowing what the next part will sound like. "He was yelling something at me, and his eyes, they… they turned black."

"Turned black?" Molly repeats dubiously, her own eyes widening. "What—what do you mean? They just… darkened, or…?"

"Black," I repeat steadily. "Entirely black… like an oil spill or something. I don't even know… it was insane. It was sort of like his pupils expanded, filled his whole eyes…"

"That's… not normal," she whispers, looking more than a little alarmed. Then she shakes her head quickly, taking a slow, shaky breath. "It's probably nothing, though. A trick of the light… right? You were both worked up…"

"It was real enough for me to come here," I point out bluntly, my fists stiff in the pockets of my jacket. She swallows, and I suddenly feel guilty for frightening her. "Sorry," I mumble, "I don't mean to… well… I'm sorry."

"You must have just been seeing things," she murmurs, and I can tell that she's assuring herself more than me. Shaking her head, she reaches out for her gloves again. "I… I appreciate you coming, but I really doubt that it's anything big… I'm sure you were just confused…"

"Probably," I half-lie. Her perspective is bringing some sense to me, though. What I saw was impossible. Another's point of view helps me realize just how crazy I really do sound—overreacting about what couldn't have been more than a tiny trick of the light. "Thank you," I add, turning to leave, embarrassment welling up in my stomach. "I just… it's stupid, I was… like you said, worked up."

"Maybe you should get something to eat," she offers from behind me. "Feed him, too… I'm sure you'll both feel a lot better on full stomachs. Good luck with him—I'm sorry he's being moody… I know what it's like."

"Right," I agree thoughtlessly, "I'll see you around."

I feel like a bloody idiot. The more I think about it, the stupider I realize I've been acting for the past half hour. There's nothing wrong with Sherlock, nothing beyond the ordinary. I tell myself as much over and over, until I feel normal again, no longer prickling with that bizarre anxiety that comes alongside impossible occurrences.

I suppose the best thing to do now is head back to the flat, apologize to Sherlock, try to get back into the flow of things. The nice, normal flow.

Normal.

That word, at the moment, is the most reassuring thing in the world.

By the time I reach the flat, my mind is on other things. The low flow of money that we've been receiving lately, the milk that needs to be bought, the ever-increasing rain that will probably be a storm by evening, whether or not Sherlock will still be angry at me. My expectations at this point are more or less to find him grouchily sitting in a corner, maybe even with the gun out and aimed at the wall—the thought brings an unwilling, stupidly fond smile to my lips, and it's with that expression in place that I saunter up to the green wooden door, reach out to unlock it and turn the handle. It creaks open immediately, and I duck in, shutting it against the pounding rain. I take a deep breath, preparing myself to confront him.

Something smells wrong.

I freeze, because the scent sets off warning signals all through my body. It takes me a long moment to identify exactly what it is, but that moment is full of dread, of creeping horror with no identifiable source. His darkened eyes suddenly seem much more real again, and the air seems to waver before me as I slowly take another step across the threshold.

"Sherlock?" I call cautiously.

Nothing.

Then it hits me.

Blood.

I'm smelling blood, and that knowledge propels me forward faster, half-running up the stairs, my feet slipping and my head spinning. Normal is suddenly very far away, and Molly's logical remarks seem foreign. A thousand imagined scenarios are running through my head, but none of them come near matching what I do find at the top of the stairs, halfway inside the living area of our flat.

Mrs. Hudson is lying face-down, thankfully, so I don't have to see her from the front. The rest is terrifying enough, though—I feel like I've been projected into some sort of bad horror film. Her back and the remains of a light lavender blouse are shredded, a mess even worse than what I saw on the table back with Molly. I gag reflexively, and my head buzzes so furiously that I stumble slightly sideways, holding myself up by gripping the doorframe. I'm seeing double, the sight of the ever-increasing pool of sluggish, deep red blood surrounding her is poisoning my vision, and I have to take a deep breath, choking on the stench that floods my throat.

Oh, God, Sherlock.

I call his name, over and over as I trip over her body, making my way into the flat, looking around frantically. It's empty but chaotic—the couch is overturned, the microscope is shattered in the kitchen, and the refrigerator door is hanging open, food and frozen body parts strewn over the table. Patches of what I force myself to acknowledge as Mrs. Hudson's blood are smeared across half the available surfaces, cutting through the yellow curve of the bullet-ridden smiley face on the wall and staining the wood of the coffee table.

Jesus…

Then I see the Union Jack pillow that I use so frequently as back support. It's not on the chair where it belongs, but rather thrown carelessly on the ground. I can't resist shuddering as I kneel down, bend in closer to see it—a scarlet handprint, perfectly clear against the blue and red stripes.

If not for this morning's incidents, I would have thought that someone had broken into the flat. But I know the door was locked—no sign of a forced entry—and I can't ignore the fact that Sherlock would never be dragged away. I wasn't gone for long—if someone else had attacked, he'd still be here, fighting.

He's the one who's done all this, and I know it.

Molly, my mind tells me, go back to Molly. My legs are shaky as hell, but I manage to make my way out again, holding my breath as I slide past the landlady's body. Her death is burning like acid in my chest, but I can't focus on it—somehow, the threat of Sherlock is a thousand times more prominent, the fact that he's out there and probably prepared to kill more, that he's killing at all. Sally Donovan's words come back to me suddenly as I stumble my way down the staircase.

One day, solving crimes won't be enough. One day we'll all be standing around a body and Sherlock Holmes will be the one who put it there.

I can't possibly tell myself that she's right, because that will be too much. Instead, I force my mind to remain completely blank as I gratefully make my way back outside, take a deep breath of moist, rainy air. I don't know what the hell's happening, but one thought is clear in my head—I have to get to Molly. I consider taking a cab, but my paranoia level is suddenly increased, and I can't help but remember Jeff Hope, the man with the pills. I can't afford to risk anything right now. Instead, I take off running, my feet pounding against the slick pavement, the air whistling by and several pedestrians shooting me strange looks as I rush in the direction of St. Bart's. Despite my best efforts, I can't keep my mind clear, and his face keeps coming back to me, the last time I saw it—pale, furious, dark-eyed.

Dark-eyed.

The rapid chills have returned, coasting one after another down my spine and assisted by the cold of rain soaking my jacket. My lungs are on fire from running as the minutes drag by, but I don't mind the pain—it helps to distract me. It's almost too soon when I finally reach the hospital, but I don't slow down, tearing through the door and ignoring surprised shouts as I make my way down the hall, not even pausing to savor the dry air until I reach Molly's door, thrust it open and half-limp in, my stomach cramping and my breath rushing rapidly.

She's still there, thank God, and so is, of all people, Detective Inspector Lestrade. She seems to be filling him in on the body that lies between them—the same one as earlier, I note abstractly, making sure to close the door behind me as tightly as possible and standing against it, my chest heaving.

"John," she exclaims, looking first pleasantly surprised, then terrified, the expressions melting into one another in the span of a split second. "What happened? Did Sherlock…"

"Mrs. Hudson," I manage to choke out, ignoring Lestrade's confused stare. "He—she's dead, Molly… he's not there, I think he killed her."

She goes horribly pale, and Lestrade lets out a disbelieving "What?"

"Sherlock killed our landlady," I rasp. "Oh, God, there's—there's blood everywhere, the flat is ransacked… I know it was him… I didn't imagine the eyes, there's something wrong with him, there's something really wrong with him…"

"Sherlock killed her?" he repeats blankly, his deep grey eyes uncomprehending. "What—what are you talking about?"

I just shake my head, pacing around the table and trying to regulate my breathing to a reasonable level. We have to catch him. Can't let him get another one. I hear Molly's voice behind me, filling Lestrade in in a hushed murmur.

"He saw something earlier… Sherlock's eyes flashed black, completely black. Neither of us have any idea what it could be, but maybe it's related somehow… some sort of obscure psychopathic illness…?"

"Could be," the policeman agrees grimly, swallowing his shock. "Did you check the internet?"

"No," Molly admits, but I'm already at the computer parked on a table in the corner of the room, clicking open a web browser, shakily typing into the search engine.

Black eyes anger murder.

It's a pathetic string of keywords, but the best my frantic mind can come up with at the moment, and I tap my foot impatiently against the linoleum flooring as the page of results slowly loads. I feel Lestrade and Molly come up behind me, but I don't turn around to face them, instead scan the list of dark blue page links that have appeared.

Makeup tutorials, racist articles, scientific examinations on how rage might induce pupil dilation…

"Is that it?" Lestrade questions, reaching over my shoulder to indicate the latter.

"No." I give my head a sharp, quick shake. "It wasn't just dilation. They were all black."

"All black?" he repeats, his voice wavering for the first time. I ignore him and continue scrolling, moving onto the second page and hissing in frustration when I begin to get repeat results. There must be something in here somewhere…

"There," Molly breathes suddenly when I move to the third page. "Second from top."

I focus on the words—demonic possession—and a chill slides down my spine. As unlikely as I know it to be, I can't resist clicking on the words, even as Lestrade's skeptical snort sounds. I expect a website with a pure black background and red words in some sort of scary-movie font, but what I get is a dull white page, sans-serif text that alarms me in its matter-of-fact brevity.

If you're reading this, if you have one on your tail, it's already too late. Give it up. Some people suggest rock salt, pentagrams, and holy water, but take my advice and accept that you're dead. The best you can do is run, but even that won't last forever. These things are damn strong, and they'll hunt you down and kill you and there's nothing you can do to put it off.

You know it's a demon when the eyes flash black in anger. The sight's unmistakable. They'll also probably leave a trail of chaos behind—murder, mutilation, the whole damn package. If the thing's after you, give up for the good of others. These are the lost souls of people who used to be human, and maybe this one just has a grudge against you. Let it do its work and save the rest of us if you've got any heart left in you.

That's all there is. I stare unblinkingly, and the utter silence filling the room is shattered only when Lestrade gives a light, clearly disbelieving cough.

"John… you know this is rubbish. Meant to scare kids or something. There's no way that a demon's in him. Hell, those things aren't even real."

"Says who?" I snap back. My voice is sharp, because, like it or not, the words really do strike a note with me. They fit perfectly—the unexpected eye color change, Mrs. Hudson's death (my stomach sinks at the memory), Sherlock's disappearance.

If the thing's after you, give up for the good of others.

Is he after me? The very thought is terrifying, and I try to push it out of my mind, taking a deep breath. "Rock salt, it says," I begin softly, turning around to face the other two. "Rock salt, pentagrams, and holy water."

"You aren't serious?" Lestrade scoffs. "A bunch of witchcraft nonsense isn't going to protect you from a psychopath! I know these people, and trust me, there's nothing magical about them."

"Greg," Molly intones gently, but he plows on.

"For God's sake, the man's probably out there looking for others to butcher—I've known Sherlock for longer than either of you, and I'd like to believe he's a good man, but if he's cracked, he's cracked! We have to do something about that—and by something, I don't mean salt, I mean men and guns and action—"

His words are disrupted by a bang as the door suddenly flies open. I whip around, my heart leaping to my throat, and throw my arms defensively in front of me in what I know to be a pointless action. But in the few moments that it takes for me to process what I'm seeing, I realize that what we're facing isn't a threat at all, but rather the results of one.

Sergeant Donovan is hunched over, her hands clutching her stomach, and I can see the horrible dark crimson stain spreading around them, marring the white fabric of her shirt. Her face is starkly pale underneath its usual light brown tone, and her eyes wide and foggy as her gaze locks with Lestrade's. Slowly, she takes a shaky, stumbling step forward, then folds forward, falling to her knees on the ground. Her hands release to break her fall, and the nausea rising inside my stomach reaches a crescendo as the blood begins leaking onto the floor—I can tell that it's only her shirt that's holding her insides in, and it's barely doing the job.

"Donovan?" Lestrade demands, the name thick with horror.

"It's… Sherlock," she manages to rasp, her voice faint and scratching against her throat. "He's… here… his—his eyes…" Then her form folds sideways, drops to the ground, and I have to reach out, grip Lestrade's shoulder to stop him from bolting over to her. The action is slow, like moving through molasses, and everything I do seems to have crept to a snail's pace.

"John…"He tries to shake me off, but I don't let up, my teeth clamped tightly together. "Let me go, we need to…"

"There's no use," Molly half-gasps.

"No—she just… we were here to check up on—on the body…" He gestures vaguely towards the body still lying on the slab in the middle of the room, still staring in horror at Donovan's corpse. "She didn't… why would he come here…?"

Sherlock… he's… here…

"We have to go," I hiss suddenly, snapping out of my frozen trance and gripping both of their arms. "She wasn't making things up—come on, is there a back door or something out of here?"

"Yes, right—here," Molly whimpers, hurrying to the other side of her room. I half-run after her, not loosening my hold on either of them as she reaches a door and slams her whole side against it, disregarding the wailing alarm that fills the air as soon as it opens. "Emergency exit," she offers by way of explanation. The three of us tumble out, and my clutch slips as the rain surprises me with its sudden, drenching iciness. I choke on the freezing air, and lose my balance for a moment on the slick pavement before Lestrade steadies me.

"The police cruiser," he calls over the rush of the heavy rainfall. "It's right out here…" He waves a trembling hand, and Molly leads the way, sloshing through puddles. I try not to think about how my mind is whirling, how everything is falling apart around me—I've reverted to my soldier instincts, and my only focus is to keep moving forward, to stay at a steady pace. Because I've somehow managed to drag Molly and Lestrade into this, and I can't let them down now.

After a few seconds, I locate the police car that Lestrade mentioned, and he steps ahead of me, fumbling with the handle until it clicks open.

"Where are we going?" he questions swiftly as he jumps in and cranks on the engine. Molly darts around and slips into the left front seat, leaving me to settle for the back. The dryness only increases the chill enveloping me, seeming to freeze the rain on my skin and the wet hair dripping down my neck. I slam down the lock of the door as soon as I'm inside and hold it there, as though such an action keeps us safer somehow.

"Away," I reply simply. "As far away as possible. You saw that website… it said we have to run."

"You believe it's a… a demon, then?" he asks with a sort of roughness, his jaw set as he grips the steering wheel. Molly glances towards him, her features delicate and still, but I can see the tears welling up in her eyes and the tremor in her hands, which are delicately folded in her lap. She's just as terrified as I am, and Lestrade almost definitely is as well, judging by the swift movement of his chest.

"You heard Donovan," I reply simply. "Black eyes."

"God, yeah… poor Sally…"

"Poor Mrs. Hudson," I retort, stung a bit. It's not that I'm not stunned and saddened by the police sergeant's death, but it's obvious enough that Sherlock would want to kill her if he did decide to go on a murder spree—after all, she was always an absolute bitch to him.

Still, I can't let myself believe that this is Sherlock. It's got to be a demon, just some demon inside of him… the real Sherlock, the one I know—he's not evil, not twisted, not a creature of Hell. And even if the thought of such a fantastical thing inhabiting his body seems admittedly a bit far-fetched, it's what I have to rely on. It's almost too good to be true, though, the thought that it's not really him, that the real Sherlock is hidden in that body somewhere…

I'll be lost if he's gone.

"Just stop it!" Molly cries, clearly detecting the aggressiveness in my voice. "Their deaths were both horrible, okay? What we have to do now—" She takes a sharp, shaky breath, and I see a single tear slip from one of her large eyes, down her flushed cheek. "What we have to do now is get ourselves out of here safely, away from… away from Sh-Sherlock."

The way she stutters over her name reminds me—she's infatuated with him. God, this must be awful for her, almost as much so as it is for me. I'm sorry, Molly… I'm sorry that this is happening to you… happening to all of us. I don't speak aloud, though, just nod to myself, deciding to keep quiet and let Lestrade handle the driving. Tension is undeniably running high between all three of us, and I don't know how long we'll be stuck together, so it's probably best if I remain silent for the time being. Trying to distract myself, I turn around and stare through the back window, half-gripping the seatbelt that I don't quite pull over myself and squinting to get a glimpse of the fading shape of St. Bart's.

The rain is pounding down, blurring my view, but I can just barely make it out—a slim figure, without the usual black coat, standing there in pale shirt and dark trousers. His hands are extended slightly, held out from his sides, and I can see all too clearly that they're dripping with scarlet. His eyes also burn—for a moment, my heart skips, because they're just as I remember them always being, green-tinted grey-blue and icy, but then his lashes twitch, and they change, suddenly deep, deep black.

Sucking in a breath, I turn around again, forcing myself to keep my gaze fixated on the road ahead.