Disclaimer: Not mine, no profit made.

Warnings: Mention of suicide/suicidal thoughts

A/N: Obviously, very AU by now.

He wakes gagging, barely has time to fling himself from the bed to the toilet, and even as he retches he wonders why he's bothering.

He said yes.

Sam leans back and stares up at the cracked, moldy ceiling with shattered eyes. He said yes, and the world paid the price. Even worse, Dean knows it. Because Zachariah didn't just take Dean with him to the future, he brought Sam too. And now Sam knows everything. Everything he did, everything Lucifer will do while wearing his body. All the hype about 2012 being the end of the world is wrong, he thinks on a surge of hysterical laughter, because apparently killing millions, maybe even billions wasn't enough for Lucifer; he was wrapping up his endgame in 2014, and killing Dean was just one of the final pieces in the Devil's grand scheme. And it's all his fault, because he said yes.

He knows why he did it. Of course he knows why.

All his life he's always had Dean. Dean was his big brother, the center of his goddamn world. Sam spent a long, agonizing year watching Dean's life slip away between his fingers, and nothing he did stopped it, nothing even slowed it down. Sam's fierce, unyielding brother told him with tears in his eyes that he didn't want to die, didn't want to go to Hell, and the youngest Winchester heard what they both didn't say: Dean was going to Hell, because of Sam.

He couldn't let that happen. So he came up with a final, desperate plan, and he actually let himself think that he could pull it off, that he could break the Deal and save his big brother the same way Dean saved him.

Except it didn't work. Except Lilith was smarter, except Cas and the rest were almost certainly playing him even then, except he walked in like a fucking lamb to the slaughter—and worse, he brought Dean with him. Dean died in fear and agony, torn apart by Lilith's Hounds and still believing in Sam. And Sam? He couldn't even get dying right. He lets his head sink forward with a moan, the porcelain cool against his clammy skin as he shivers, thinking back to that insane, desperate time without Dean.

A lot of the four months are a blur. He has vague memories of clutching Dean's cooling corpse, voice gone from his screams of agony. Burying Dean is a knife-edged memory that's never faded. Sam did it himself, dug the grave and built the crude cross at the top, in a sweet little meadow outside of Pontiac he figured nobody would ever find, much less disturb. Bobby wanted the younger hunter to burn Dean, but he didn't listen; he buried his brother instead and hit the road. Tried everything he could think of to trade himself for Dean and failed miserably at them all. Spent at least half the time dead drunk and the other half doing his damndest to kill himself. Probably would've pulled it off, except for Ruby. And he, sucker that he was, fell for her little spiel. She pulled him out of his personal Pit, kept him afloat when he didn't even want to swim. Then she made damn sure he'd never make it to shore again. And he fell for it.

Sam swallows thickly. His throat burns, his mouth tastes like a sewer and his knees ache against the cheap, cracked linoleum he's been kneeling on for way too long, but he ignores it all, too lost in his anguish to give a damn about a few aches and pains. He fucked up and in so many, many ways. And yeah, he had help doing it, but that doesn't change anything. The hunter wishes briefly that he'd managed to die that first time, when a demon had damn near gutted him because he didn't bother ducking in time, and he woke to blood in his mouth and Ruby glaring down at him, a bandage white on her arm. Wishes he'd had the courage to end himself long ago, before he fucked the world over.

He has the courage now. And better, he knows where the Colt is, thanks to Zach's time warp and being stuck in Lucifer's head. It can kill anything. Anything supernatural. Even something caught somewhere between mortal and demon like Sam himself.

Besides, he turned up a lot of shit during his year trying to save Dean's ass. Including some mega binding spells. Ones that should even keep Lucifer away from his body, which means his soul can't get shoved back in. A dead body isn't going to be much good, even for the Lightbringer himself. Death isn't consent, after all.

He can do this. He will do this. It's the least of what he owes the world. What he owes to Dean.

The surge of determination brings him to his feet. He absently flushes the toilet clean, grimacing briefly at the stench, and even more absently swishes water around to get rid of the truly foul taste in his mouth before he heads into the main room. It's a wreck, clothes tossed haphazardly around, backpack and weapons spread across the other bed he got out of habit, as if to hide how empty it is. Sam's eyes run briefly over the mess before he finds what he's looking for, the small and battered journal he recorded his research in so Dean wouldn't find it. He pulls it free and sinks down to the table, absently grabbing the Styrofoam cup sitting next to the computer as he thumbs through the dog-eared pages until he finds the right one, then takes a swig of cold coffee as he skims down the page, double-checking the ritual against his memory. Then he chokes and spits the coffee back out, barely missing his laptop. He peers into the cup and winces at the filmy surface with just a hint of mold coloring the top. How the hell long has it been sitting out, anyway? Two days, three, tops? Dean would've laughed his ass off if he'd seen Sam spitting out one of his precious frou-frou drinks, and the smile pulls briefly at his lips before he gets flattened by the image of Dean, sprawled and unmoving at his feet, eyes open and gray, color leached away by death.

Dean. God. He killed his big brother, five years in the future. If that wasn't bad enough, he saw the disgust and the hatred in Dean's eyes before he died, heard it in his voice when he spoke to the Fallen angel wearing Sam. And he knew that it wasn't just aimed at Lucifer, knew Dean was even angrier at his kid brother, because he was the one who gave his consent.

He wonders if Dean's saying yes to Michael right now, as Sam dumps his moldy coffee dregs down the drain and rinses the last traces away. He hopes to God Dean is. Because it wasn't Lucifer, not all the time. Because Sam managed to get one little bit out. Managed to push Dean's buttons the way only a little brother can. Told Dean that he wouldn't change anything, so they'd end up right back here. Please, God, let it have been enough. If Michael has any sense, the first thing he'll do is come for Lucifer's vessel. The angels don't give a shit about human life, they've proven that time and again, and taking Sam down weakens Lucifer. Lucifer said it himself: Sam's his perfect vessel. Others exist, sure, but they won't be quite as good, and that's a much-needed edge for the good guys.

He rummages through his backpack, comparing the herbs to the list and checking to ensure the chalk is still intact. He'll only get one shot at this, so he'd better make it count. If he's lucky, Sam won't need the archangel, he'll pull this off himself. But it never hurts to have backup, Dean taught him that. And—he's selfish. He knows it won't bother Dean to pull the trigger, not now that he's seen what Sam will become, but Sam doesn't want his last sight to be the hatred on his big brother's face.

It has to end. But God willing, it doesn't have to be Dean to do it. He can't make amends for any of it, but he can at least spare Dean some of what's to come.

He knows why he said yes in Detroit, some time down the road. He knows exactly why. Because Dean turned away, Dean said they should stay away from each other. Because Dean is all Sam has ever had, the one person that mattered the most, and Dean doesn't want anything to do with him anymore. He deserves it, he knows he does. But when Lucifer told him that he was the perfect vessel, a tiny part of him, nearly stifled beneath the horror and the fear, cheered. Not because he wants Lucifer in him, God, no, but because there was no way Dean would turn his back now, even if only to keep his enemy under his watchful gaze.

And Dean said no. Dean said to stay away. Dean didn't say he loved Sam, didn't say he cared.

Dean said goodbye.

Something in Sam curled up and died when the phone went dead in his ear. Oh, yes, he knows why he said yes. Because he had nothing left to lose, because he had no other way out, and because a nasty little piece of him wanted Dean to hurt the way he made Sam hurt.

Because Lucifer promised the pain would stop, and Lucifer doesn't lie. Sam knows why he said yes. And he knows that eventually his determination will fade, once these memories aren't quite so fresh and raw. Right now he's still saying no, but if Lucifer finds him again, if Lucifer weaves that sweet, seductive web—he's weak, he always has been, and that all-important yes might just slip out despite his best intentions.

It's not a risk he'll take.

He has to be stopped, here and now. Firmly, permanently, and in a way that ensures Lucifer can't carry through his threat and stuff Sam right back into this meat suit until Sam says yes just to make it all stop.

What did Dean say? "The cockroaches he'd been squashing all his life." Yeah. That pretty much says it all. But Sam's not gonna make his big brother squash this one. Not this time. He can do this much for Dean; it's the least of what he owes the brother he adores.

It'll only take a few minutes to set everything up; he's made sure to keep a stock of the materials he needs on hand, just in case. Once he has the Colt, he'll be good to go in under an hour for the ritual, an extra twenty minutes added in to find someplace isolated enough that a gunshot won't draw immediate attention. The Colt will take a couple of hours to find, but that doesn't matter. But first—Sam bites his lip, considering. He doubts Dean wants to hear from him after, well, everything, but he can't just go, can't leave Dean wondering.

And he needs to apologize one last time, and hope that, someday, Dean will forgive him.

Sam's fingers tremble as he reaches for the phone, pulls up Dean's number. Speed dial one, now and always. He takes a deep breath, blows it out and sucks in another, trying to drum up the courage. This is the hardest part, he realizes, saying goodbye to Dean, accepting that his brother's given up on him completely. He doesn't want to hear the disgust that'll fill Dean's voice. He doesn't want to, but he owes Dean this and so much more.

He shuts his eyes. Now or never, Sammy. Time to suck it up, stop your whining, and pay your goddamn dues. Then AC/DC sounds, the ring tone he put in for Dean's phone because he couldn't pass it up, and his eyes snap open again as he gapes at his phone. The hell? He cautiously peers at the display: Dean, in big letters on the glowing screen.

Huh.

He's tempted to ignore the call, but he doesn't have it in him; he'll always answer Dean and he knows it. Part of being the baby brother, he supposes; Dad he could and did ignore once or twice, but never Dean. Ever.

He gathers the tattered remnants of his courage, swathes it in what little is left of his pride, and answers.

"Dean." He's vaguely proud that his voice doesn't shake too badly, even if his throat closes as soon as the word's out.

"Sammy. Oh, thank God."

Sam blinks, lost again, because he's been braced for hatred that would crush what's left of him, and instead Dean sounds—relieved? He pulls the phone away for a suspicious look at the display, but it's reading five bars, loud and clear. Maybe Dean's connection is the faulty one? Or maybe, just maybe, he's lost so much of himself that he can't even read his big brother anymore. One more sin to hold against himself, he thinks wearily.

"Dean," he repeats quietly as he sinks into the chair, legs refusing to hold him up right now. "I'm sorry." There's so much he wants to say, but that's what it boils down to in the end. Sorry for being such a fuck-up. Sorry for letting himself get hooked on demon blood and the idea that someone cared, even if she was a hell bitch. Sorry for getting so lost in vengeance and then the need to keep Dean safe that he fell hook, line and sinker for Ruby's crap and the shit the angels threw at him.

Sorry for not having the courage to take himself out of the game rather than being sickly relieved Dean wasn't following through on his message, that he was letting Sam live regardless of his reason. Sorry he hasn't had the guts to do this before, sorry he said yes to Lucifer somewhere down the road.

Sorry that he's leaving Dean alone to clean up the mess he started.

"Sammy." Dean sounds tired, which is too damn familiar, but he also sounds a little sick. That's not typical of him. "Don't, okay? Just—don't."

Don't what? Sam frowns. "Dean?"

"We need to meet, Sammy. Now."

Oh. Dean's still Dean, he's pretty sure of that, but maybe he's decided to take the other option. Kill Sam himself instead of letting Michael do the honors.

"It's okay, Dean," he says softly. "I figured out a way."

"Figured out a way to do what?" Dean sounds wary, but Sam can't blame him for that. Not now. His plans don't exactly have a good history of working out the way he intends, after all.

"I can't kill Lucifer, but I can weaken him. Without me, he'll keep burning through his vessels. It's a chance."

He'll remove the perfect vessel and a weakness in Dean's armor at the same time. Win-win for the good guys.

"Oh, hell, no!" Dean—sounds upset. Sam blinks again, utterly bewildered. Surely Dean can see why this is necessary after what he saw in the future. "Sammy, don't you dare!"

Sam's mouth drops. He knows that tone—Dean's beyond furious right now, and scared shitless too. What the hell?

"Dean, this makes sense," he argues. "You know that."

"We are going to meet." Dean sounds like he's speaking through clenched teeth, and man, is he pissed off. "You and me. You are not going to kill yourself. You're going to pack up and hit the road, right fucking now. You hearing me, Sammy?"

"Dean, I—"

"No. That is not an option. Pack. Now, Sam."

He's obeying before he even thinks, too conditioned to respond to that tone to do anything else. He's wrapping his laptop in dirty clothes and easing it into his backpack even as he argues, padding the computer with still more clothes before he starts working through the rest of the room, gathering up random bits and pieces scattered across it. That particular 'you WILL do as I say' tone is a trick Dad's never quite managed, and one Dean's always had.

"It'll work. I have a spell that'll keep Lucifer away from my body. If he doesn't have consent, he can't take me," he explains, discovering a spare sock under the bed and frowning at it before he shoves it into the backpack too and begins the hunt for his shoes.

"I don't care. Write this down." He rattled off an address, then directions which Sam scrawls down. "Got it? Good. Now promise me you'll meet me, Sam."

He doesn't want to. He doesn't want to face Dean. He doesn't want the hope stirring deep within, the small part of him that's insisting Dean would never, ever hurt him, because he's not stupid. This is war, sacrifices have to be made and he's the obvious one.

"Sam. This is not a negotiation. Promise, right fucking now."

But Dean's asking him, and he's never quite gotten the knack of saying no to his big brother.

"Sam!"

"I promise."

Dean's voice is softer now. "Good boy. Now get a car and start driving. I'll be waiting at the end."

He doesn't let the hope rise even as he obeys. For all the mess he made, he doesn't actually have all that much to pack and most of that's already done while he was talking to Dean; he didn't take much with him when he left, so he's quietly closing the door behind him in minutes. He checks out, then tosses his backpack into the car he stole, fires it up and pulls out. Sam tries not to think during the hours of driving, just follows Dean's directions until he pulls up by the side of an overpass, the Impala a familiar dark shape in the tall grass, and Dean leaning against the side, watching him come.

Sam pulls up, shuts down the car and gives himself thirty seconds before he peels himself out of the car, hands sweating as he approaches, waiting for Dean's reaction. He freezes briefly at the sight of the knife, held casually in Dean's hand. Even if he's not a demon, that knife will still kill him; it's nearly as good as the Colt and it can strike a mortal wound like any mundane weapon. He might even be contaminated enough that it'll react as if he was a demon, burn him up from the inside out.

He looks Dean in the eye as he stands there, waiting for the bite of the blade, waiting for death or salvation, because there's no longer a difference between the two, not for him.

Then Dean flips the blade and offers it to him. And Sam knows that somehow, he'll get through this. They'll get through it, together.

Dean trusts him. Dean believes in him.

That's enough.

FINIS