Title: Thicker Than Water
Summary/Prompt: Prompted by the lovely and talented rainylemons (aka pkwench) at the Dean-focused h/c meme over a hoodie_time. Season 4 - Know how Dean took issue with Sam's whole blood junkie problem? As well he should, yes. But, here's the thing - he and Sam get cursed and wake up in the morning in the wrong body - Sam in Dean's, Dean in Sam's, and Dean has this itch, this hunger, this salivation, that won't go away. He can't stomach a burger or a steak or meat because it just makes everything worse, but life's life and a job's a job, so they keep working. But, when all's said and done (with the job, not the curse) and Dean goes for a beer and Sam elsewhere, in comes Ruby. And God does he ever hate her on so many levels, but she smells so good and he wants what's under her skin. He needs it. He has to have it. If you want to make me really happy and be a total bastard, you can flip them back and leave Sam with suffering the drying out in the panic room ordeal so that Dean has angst.
Warnings/Spoilers: NC-17! Holy shit, pkwench made me write sex. IDEK. /o\ Anyway, brief het which is totally not about the sex but is sex nonetheless. Dean/OFC. Bloodplay (JFC!). A fair bit of swearing. ANGST holy crap! Demon blood addiction and attendant nastiness. Spoilers up to 5.15 inclusively.
Wordcount: 4,217
Neurotic Author's Note #1: Umm, dear pkwench, this is your prompt in spirit only. Ruby wanted NOTHING to do with this fic, and it ended up in late Season 5, and... um. It's sort of what you wanted?
Neurotic Author's Note #2: Holy Jesus F. Christ. I have NO idea where this came from, except that when I started out it was totally not going to include sex and kinky sex at that and... *cringes* I will be over there in that corner, wibbling frantically if you need me.
Neurotic Author's Note #3: Written in the wee hours of the morning today in between calls at work. Right after I finished other comment-fics, actually. No beta, nada. Zip. Zilch.

Forty-eight hours. That's all it is. They looked up the curse, and it sucks, but it's only forty-eight hours long (give or take, these things aren't an exact science), and they can totally wait that long. Except it's weird to look at Sam and have it be like looking into a mirror. A mirror with a bitchface filter, granted, but still a mirror. And, okay, Dean might have freaked out a little bit at not being in his own body anymore, but he's better now and they still have a job to do. Supernatural fuglies to hunt, people to save, apocalypses to avert, all that jazz.

It's actually kind of funny, for a little while. Sam bitches about Dean's body being constantly hungry and horny —how the hell do you manage to concentrate on anything?— and Dean trips over Sam's stupid giant feet and doesn't fit right behind the wheel of the Impala and laments having to wear one of Sam's ugly-ass shirts.

It stops being funny when they stop for breakfast, and Dean cheerfully orders himself a plate of eggs with sausage and bacon, and the taste of meat in his mouth almost makes him gag. He stares disbelievingly at his food, feels his stomach lurch, and swallows half his glass of orange juice to wash the taste away. For the first time since they woke up, he realizes that apart from the whole weird oh-my-God-I'm-not-in-my-body feeling, he actually feels, well, off. Like there's something missing, or... he's not sure how to even describe it. It's kind of like being hungry, like when he's craving steak, only not, and he drums his fingers on the table, trying to work it out in his head. Sam is looking at him, and if Dean isn't careful his little brother is going to put wrinkles on his very attractive face, so he forces himself to finish everything on his plate.

"There's no point going to Bobby's about this," he says, trying to cover for the fact that his stomach is performing cartwheels. "It'll be over soon enough, and after that whole... thing," he twirls his hand in an attempt to encompass the whole Bobby's-dead-wife-coming-to-life-and-dying-again fiasco, "I think he probably doesn't want to see us. We can stick this out, finish the case."

Sam nods. "So. More demons, you think?"

"Reasonable enough. The signs are all there. If we're lucky, no horsemen." He rubs his hands on his jeans, nearly knocks one of Sam's stupid pointy elbows against the table. "God, how do you even move in this body? It's like it never ends!"

Sam snorts. "We should split up, cover more ground. Give me the cell phone in your pocket."

"What? Why?"

"Which cell phone number do you know by heart? Mine or yours?"

"Good point," he hands over the cell phone, takes his back from Sam. Himself. Whatever. God.

By the time lunch time rolls around, Dean is coming out of his skin. Or Sam's skin. There's a constant gnawing feeling in the pit of his stomach, nagging at him to the point where it's impossible to concentrate on anything at all. He interviews witnesses with half his mind on the job at best, ends up retreating into the men's room of the bar he's been canvassing and ducks his head under the tap. It's only when he raises his head and his hair drips all over his shirt that he realizes what a really bad idea that was. He manages to dry his hair a bit with paper towel, and begins to appreciate just how much work it is to have hair this long. No wonder Sam never has a good hair day.

Sam is still hip-deep in research when he calls, and so Dean ends up at the diner alone, just him and the empty gnawing feeling. He orders a steak, rare, eats the whole thing in record time —and just how does Sam ever manage to survive on salad?— and the feeling gets even worse, complete with a brief spate of hot-and-cold flashes. His palms are sweaty, and it's not the regular kind of Sam-sweat that he's accustomed to seeing on his brother all the time. At least, he doesn't think so. He wonders if Sam was coming down with something before they switched bodies, like a stomach flu or something. He gives himself the afternoon off, on a whim, goes back to the motel room and fishes out the thermometer from the first aid kit. Normally he wouldn't be caught dead with a thermometer, but he's in Sam's body and Sam loves shit like this, so he figures it doesn't count.

There's no fever. Sam always runs a little hot, so a few percentages of a degree above normal totally doesn't count. He sits on the edge of the bed, staring at the reading as though it'll spontaneously provide him with the answers to all his problems. He should just call Sam, figure out where they are with the case, and keep going, but he's kind of feeling screwed up right now and all he really wants is a shower and a nap. He decides on the shower, but not the nap. Compromise, because Dean Winchester is all about being reasonable.

The shower doesn't help, either, and when he's out and wrapped in a towel, dripping on the motel carpet and rummaging through Sam's things for a pair of clean boxers, someone knocks at the door to the motel room. Sam wouldn't knock, so Dean stands back a bit when he opens the door, revealing a very pretty blonde girl in a sparkly blue tank top, blue jeans and high tops. She smiles, revealing very white, even teeth behind soft pink lips. She smells wonderful.

"Hello, Sam." He takes a step back in spite of himself, and she follows him inside, taking a look around. "You're a difficult man to find, Sam Winchester. It took all sorts of favours to find you."

He swallows. "Christo."

Her eyes flicker black, then back to blue, then roll toward the ceiling. "Oh, we're being all formal now, are we? And here I thought you broke that salt line on purpose."

Not for the first time that day, Dean finds himself cursing Sam's stupidly large and unwieldy body. It's like trying to manoeuvre a Clydesdale with poor fashion sense. He's been caught with his pants down, quite literally. "What you want?"

The demon smirks. "It's not about what I want, Sam. It's about what you want."

She steps toward him, runs her hands suggestively over her hips, and fuck him, but he wants her. He doesn't understand it, feels his stomach coil in revulsion, but his brain has short-circuited and the only thing he wants is to grab her and throw her to the floor and sink his teeth into the flesh that joins her neck and shoulder and lick and taste... His heart is thudding against his ribcage, and he swallows hard.

"No," he manages to say, but it's strangled and unconvincing, even to his own ears.

The demon throws her head back and laughs. "Oh, Sammy. You and I both know that's not true. Here's the deal: I'm going to hang around. You won't see me, but I'll be here. Think of me as a little cash advance from my Daddy, for when you eventually come around to seeing things his way. It's inevitable, and we both know what you really want. You think about that. Take your time. I wouldn't mention it to your brother, though. You know how he feels about your little... problem."

It's ridiculous. He's alone in a room with a demon with no protection except a cheap, flimsy motel towel, and he's completely unscathed. This never happens in the world of Dean Winchester. He gapes incredulously as she saunters out with an exaggerated swing of her hips, and is grateful when his knees give out and force him to sit on the nearest bed, because it's the only thing preventing him from running after her and dragging her back in here.

Dinner with Sam is a strange, strained affair. He's distracted, can't rid himself of the image of the blonde demon —he doesn't even know her name, he realizes. Every time he closes his eyes she's there, and he can practically see her pulling up her shirt, imagines himself slicing neat, shallow cuts into the smooth skin of her breasts and lapping at the blood there. The fact that he's fantasizing about her blood at all makes his stomach churn and his heart race, and he keeps wiping his hands on his jeans legs, drinks a lot more water than he usually does, and brushes off Sam's concern with a comment about Sam's freaky physiology that's probably a lot nastier than it really needs to be. Sam makes a bitchface —using Dean's face to do it, no less— but lets the matter drop.

Night time doesn't bring any relief. To the contrary, there's nothing to distract him from the craving, from the images of the blond demon stretching out over him. He's half-hard already, digs his fingers into the mattress because fuck this, it cannot be this fucking arousing to think about some girl slicing open her wrist and dribbling blood into his mouth. He licks his lips, gets up and paces as quietly as he can manage, lies back down when it does absofuckinglutely no good. Under normal circumstances he'd just take care of the problem —it's mechanical, after all— but this is Sam's body and it's just way too weird even by their standards. He bounces out of bed again five minutes later, heads into the bathroom and takes the coldest shower he can stand.

Sam looks at him strangely the next morning, and he realizes that he —Sam's face anyway— must look like utter shit. "You okay?"

He shrugs. "Slept badly."

"I thought I heard you taking a shower. Any particular reason you slept badly?"

He starts guiltily. "What? No! Why would you think that?"

Sam rolls his eyes. "Jeez, touchy. It's just that I'm used to certain things about my body, like the fact that my back and my knees hurt pretty much fucking constantly, but I thought maybe that's what kept you up."

Dean relaxes a fraction. "Oh. Well, no. They actually don't hurt right now." It's the last of his problems, he thinks ruefully, and rubs at his eyes with the tips of his fingers as the image of the pretty blonde demon flashes in his mind's eye. He thinks he might be going crazy.

"Okay, well, good. I was just worried. That's my body you're screwing with, you know," Sam quirks a smile at him. "Another day, and it'll all just be another funny story for later on. We just have to make it through today, go to bed tonight, and by the time we're awake tomorrow it'll be done. Piece of cake."

Dean fights the urge to snort. Piece of cake for Sam, maybe, but he's not sure how he's going to make it through the next ten minutes. He's almost pathetically grateful when Sam suggests splitting up again, because all he wants to do is go back to the motel room and curl up on his bed and wait for the nightmare to be over. It's not all he wants to do, if he's honest with himself, but it's the one thing he wants that isn't horrifyingly wrong and sick and depraved. He makes a half-hearted attempt to track down one of the leads, but he already knows who the demon is, even if he lied to Sam about her (oh, fuck, he lied to Sam about a demon), and it all seems kind of pointless. The world seems dull and muted around him, and he wanders aimlessly around the town for the better part of the day, unsure what to do with himself. He ignores Sam's call around lunch time, lets it go to voicemail. He finds himself drifting back to the motel room seemingly in spite of himself, tells himself it's because he's tired, and for no other reason.

The demon is waiting for him when he arrives, draped over his bed, head propped up on one well-manicured hand. He never fixed the salt line, and Sam must not have noticed. She's dressed in an obscenely short white dress with low cleavage and no sleeves, and she draws up a leg enticingly as he comes in, revealing blue veins just under the delicate skin of her inner thigh.

"I knew you wouldn't disappoint, Sammy," she purrs.

He should kill her. He has the demon-killing knife, he has salt and holy water and he knows three exorcisms by heart if all else fails. He takes a step toward her, heart in his throat. She bares her teeth in a feral grin, licks her lips, and reaches for a tiny pocket knife on the bedside table. She flicks it open, traces the point delicately down her chest, into her cleavage, and he's suddenly, blindingly hard. She chuckles at the moan that tears right through him.

"Come on, then. You can have it. I'm all yours."

The tiny pocket-knife digs deeper into her skin. Blood wells in the shallow cut, and whatever semblance of self-control he had left crumbles away. He takes a faltering step toward the bed, then another, and the next thing he knows he's straddling her hips, the hilt of the knife pressed into his palm, carefully cutting parallel lines into the creamy skin beneath him. Beautiful. He finds himself murmuring under his breath, nothing that makes any sense, just knows that he wants this more than he's ever wanted anything in his life. She throws her head back with a moan, and she unzips his jeans, snakes her hand into his fly and jacks him with sure, practised strokes as he applies his tongue to the cuts he's just made.

The feeling is incredible. The blood is warm in his mouth, tastes of salt and copper and sulphur, the pungent scent filling the room and making him dizzy with want and need. It's heady, intoxicating, and he feels power surging through him even as he fucks into her hand, shaking and sweating and feeling like he's being ripped apart from the inside out only it's all coming together in a swirl of red against white. He bites down on her shoulder, right at the base of her neck, just like he's been picturing for the past day, feels the flesh yield beneath his teeth, and his eyes roll back into his head with the sensation.

"That's it," the demon gasps, writhing beneath him, "that's it, baby. You're almost there. So close, you're almost there, come on!"

He almost doesn't recognize his moans as coming from him, lost in the dual sensations of her hand around his cock and her blood in his mouth. He feels her speed up her motions, matches the thrust of his hips to her rhythm, swallowing convulsively as he teeters on the brink of climax. She keeps him there what feels like an impossibly long time, caught in the moment like an insect in amber, murmuring blandishments in his ear and opening herself up to him like a tainted flower, and he finds he doesn't care, doesn't give a fuck so long as she keeps doing it, keeps going, and the desperate rhythm of his hips falters, stutters frantically.

"Dean!"

It's his own voice, coming from the wrong side of the room, and he barely registers it. He comes so hard that stars spark behind his closed eyelids, and the next thing he knows he's being flung against a wall, head snapping back with a jarring crack. He slumps to the floor, boneless and shaking, has just enough presence of mind to tuck himself back into his pants. The demon is up, her white dress smeared with streaks of crimson, and he sees himself —Sam— lunge at her and bury the knife in her chest. She shrieks, hellfire spewing from her eyes and mouth, the light guttering like the flame from a candle before it extinguishes itself completely.

For a moment everything is terribly, horribly still. The gnawing sensation is gone, and it feels like electricity is coursing through his veins. He looks up at Sam, opens his mouth, and finds he doesn't have the words. He stares at his own face looking back at him, and his heart lurches painfully in his chest. Is this what Sam saw, all those times? The disgust, the disappointment, the betrayal? Mostly, what he sees reflected back at him is pain, and the only thing he wants now is to wipe that look off his brother's face, to take it all back, except that his legs won't hold him up and there's fire in every single part of his body. Right now, Lucifer himself could walk into the room and Dean is pretty fucking sure he could take him. Except that it's all a lie.

Sam comes toward him, all but falls on his knees next to him, lets his head drop. He reaches out with one hand, brushes the hair out of Dean's face. He swallows, takes a deep breath. "Okay, Dean. Let's get you cleaned up."

Dean's vocal cords start working again. "God, Sammy, I'm so sorry..."

Sam nods. "I know," he says, and his voice is wrecked. "I know you are. Come on."

Dean lets Sam pull him to his feet, all but collapses against him. "I'm so sorry," he says again, as though somehow that'll make it all better. "God, Sam... is it always like that?"

He clutches at Sam's shirt, lets himself be half-carried, half-dragged into the bathroom, falls to his knees. Sam has just enough time to lift the toilet seat before Dean grabs the bowl with both hands and pukes up his stomachful of blood. He stays kneeling, retching miserably until long after there's nothing left to throw up, is pathetically grateful when Sam places a cool washcloth on the back of his neck.

"Okay. We're gonna clean you up now." Sam strips his clothes off, runs the bath, and all but lifts him into it. "How much blood did you drink?"

"I don't know," he moans, shakes his head. "Sammy..."

Sam pets his hair. "Shh, I know. I know. I'm sorry too, I should have realized, should have seen what it was doing to you."

"Is it always like that?" he asks again, shudders as Sam wipes him down with a washcloth, the last of the blood dissolving in crimson eddies in the bathwater.

"Mostly."

He whimpers. "God, how do you do it? I could feel it eating away at me and I thought I was going to lose my mind..." he thinks there might be tears in his eyes.

Sam just keeps wiping his face. "I dunno. I guess I'm just used to it by now. It's always there. I just ignore it."

When Dean is clean again Sam drains the tub, hauls him out and wraps him in a fresh towel, seats him on the toilet before rubbing him down. "You're right," he remarks mildly. "I am freaking huge. No wonder you can never hold me up when I fall over. You think you can make it to the bed if I help you?"

He nods, lists against Sam as he pulls him to his feet. "'M so tired, Sam. Cold."

"Yeah, that's normal, since you puked up most of the blood. You're kind of going to have a shitty night, I'm afraid."

Dean curls up on his bed with a quiet moan. He can't see how this can get any worse, until it does. Sam sits next to him, rubs a hand between his shoulder blades as he shivers, racked with alternating hot and cold flashes, teeth chattering, stomach cramping horribly. The demon is still lying dead on the floor, blue eyes vacant and staring at him, and he must say something because the next thing he knows Sam is wrapping her body in a sheet and rolling it under the other bed, where neither of them can see it.

"We'll be long gone by the time housekeeping finds her, poor thing," Sam comments, and Dean closes his eyes, thinks he might be sick again.

By the time night falls the fever has taken over completely, and he shivers and sweats and whimpers, keeps drinking as much water as Sam can coax into him. Sam wipes him down with a wet washcloth, strokes his hair, and spends a lot of time playing the 'five-minute game' with him.

"It's easy enough," he explains quietly. "You look at the clock, and you tell yourself, I'm going to last five more minutes. Because anybody can last five minutes. So you watch the clock, and you wait five minutes. And then you start again. As many times as it takes. It's okay," he says when Dean moans. "I've done it lots of times. I'll help you."

So he counts. One minute. Two minutes. At five minutes he starts again, feeling stupid. But the next thing he knows an hour has passed, and then two. Sam counts with him, laces their fingers together, gently wipes the tears away from his face when the pain and shame get too intense. Dean gets the sinking feeling that this is all stuff Sam would have wanted for himself when he was detoxing and never got. Both times. At one point Sam leans forward.

"You're going to have to drive us to Bobby's in the morning."

He lifts his head a fraction of an inch off his pillow, which is smeared with tears and drool and maybe a little snot. "Wha'?"

"We're going to be switching back in a couple more hours, give or take. So you have to drive us to Bobby's, and lock me down. Understand?" He whimpers as another cramp bends him double, but Sam shakes his shoulder, hard. "Dean. Do. You. Understand?"

"Yeah, yes. I understand."

Sam huffs what sounds like a sigh of relief. "Good. Try to get some sleep, okay?"

Dean manages a nod, curls up tighter under the sheets. He's never going to be able to sleep, he thinks, not like this. He might never sleep again. He scrunches up his face, eyes closed, and eventually, in spite of all his expectations, darkness does close in on him.

It's disorienting to awaken somewhere completely different from where he went to sleep, and uncomfortable. He's sitting half-slumped in an uncomfortable wooden chair, his muscles cramped up from being in the same position for too long. He sits up, a little groggy, but all the terrible clenching, gnawing, crawling sensations from the day before are gone. He looks down at his hands, is overjoyed to find himself looking at his own familiar fingers, complete with silver ring and wooden bead bracelet. He feels a grin threaten to split his face in half, because goddamn is it good to be back in his own body!

There's a quiet whimper from the bed, and he blinks, shakes himself out of his sleep-induced stupor to lean over and check on his brother, who's curled up under a single thin white sheet, eyes closed, sweat pouring from him, soaking the bed. His face is flushed, the circles under his eyes like bruises, his lips moving soundlessly.

"Shit, Sammy," he mutters, remembering their earlier conversation. He glances at the other bed, still unmade and covered in blood and other fluids he doesn't really want to think about, and swallows the sudden urge to vomit all over again. He turns back, brushes back Sam's hair, remembering how good it felt when Sam did it for him. "Hey, you with me?"

Sam's eyes flutter open, but his gaze is glassy, unfocussed. "D'n?"

"Yeah, that's right. How you feeling?"

"Sh'tty."

He bites his lip. "I'm so sorry, Sammy, but we have to go. I'm going to take you to Bobby's, get us both properly looked after. You think you can walk if I help you?"

With what looks like a superhuman effort Sam pushes himself upright, all but collapses into Dean's arms, resting his forehead against his collarbone. "You owe me forever," he mutters, holding onto Dean for all he's worth. "I mean it."

Dean wraps his arms around his shoulders. "You got it, Sam. Anything you want."

"Anything?" Sam sounds like a little kid.

"I said so, didn't I?"

"I want a pony."

Dean snorts in spite of himself. "I always knew you were a girl," he says, holds on a little tighter when all of Sam's muscles go rigid with the first of what's likely many spasms to come. "Okay, c'mon. I got it from here."