A/N: I know that I have no business starting another story when I am already working on 2.5 other long ones, but inspiration strikes when it strikes, and this one would not leave me alone. I wrote it for Unattainable Dreams's June Prompt Exchange. It's a bit different from my usual style, but I like the way it turned out. It will have four chapters eventually, and I am almost finished writing it, so it should be updated fairly regularly. I should warn you that it is a death fic, but it does have as happy an ending as possible, and I would urge you to give it a try. Enjoy!

Disclaimer: If I owned Supernatural, Dean wouldn't be in this mess.

Chapter 1

Sam's gut lurches slightly as he meets those horrific black eyes, so wrong when they are staring out of that familiar face. It strengthens his resolve though, and he slips the first needle into the neck of the demon that had once been his brother. He presses the plunger down and watches his blood disappear into Dean's body. The demon just smirks at him arrogantly.

"You know this won't work, right?" he hisses, and Sam wishes that he'd had the strength to gag him when he was chaining him up. He had been too stunned and horrified and lost though.

The feelings that assaulted Sam when he went to check on Dean's body after the failed summoning were indescribable. A wild, irrational hope surged through him when he saw his brother standing up, back turned to the doorway as he surveyed his surroundings. Sam said his name, and though the word had come out little louder than a whisper, Dean heard it. He turned, and the sight of his black eyes shattered every tentative hope of Sam's, and hit him like a battering ram to the stomach. He said Dean's name again, but it came out as a gasp of horror.

"You're wrong," Sam tells the demon, withdrawing the needle once the syringe is empty. You have to be.

He walks over to sit in the other chair that he has brought into the dungeon, and he can feel Dean's inky eyes on him, though he refuses to meet them.

"Even if you could cure something like me, which you can't," the demon persists, and Sam closes his eyes as if that could shut out the sound of a monster talking to him with his brother's voice. "We both know you won't go through with it. It's still the third trial, and it'll still kill you. You said yourself that you wouldn't die for me, and I doubt that's changed now that you don't even think I'm me anymore."

Sam keeps his eyes shut, but he cannot stop the grimace at Dean's words. As if he has not been regretting that conversation enough already, as if the knowledge that his brother had faced Metatron believing that Sam would not be bothered by his death was not tearing at his heart as it was. He does not need his words thrown back at him by this twisted parody of his brother.

Dean blinked his eyes back to normal and gave Sam a smile, and for a few stupidly naïve moments, Sam let himself believe that the situation was not too bad. Dean was alive again, and they could work through this new symptom of Cain's mark. But then he noticed the cruelty in the smile, and when Dean spoke, his hopes were dashed anew.

"Well, if it isn't Mr. Useless," the demon snarled, and he sounded so unlike Dean that Sam could no longer doubt that the brother he loved had been eclipsed by what he had become. "What's the matter, Sammy? Don't like the new eyes?"

His eyes flashed back to black, and he laughed coldly when Sam took an involuntary step away.

"What happened to you, Dean?" Sam asked. His hand strayed to the pocket that held Ruby's knife, but something told him that it would not work on whatever Dean had been twisted into.

"The damnedest thing," Dean replied, advancing slowly on Sam the way a predator would on its stunned prey. "I was set free."

"Free from what?" Sam whispered as he fought against his instincts and held his ground.

"Humanity."

Dean continues to shoot barbs his way, but Sam just works to tune him out. He is unsuccessful, but at least he does not give the demon the satisfaction of a verbal response. The first hour seems to drag on interminably, but finally the alarm on Sam's watch beeps, and he prepares the second syringe of blood.

Dean meets his eyes as he approaches, and they are back to green. Sam has to look away from them as he inserts the needle again; it is too painful to look into Dean's eyes and not see his brother staring back at him.

"Why even bother with this charade?" the demon demands. "Is it so that you can give yourself points for pretending to try? Do you really think that'll make you feel better when you fail?"

Sam goes back to ignoring him, but he turns his chair away from Dean this time so that the demon will not see the tears gathering in the corners of his eyes.

"Do you have any idea how liberating this feels?" Dean asked as he took another step toward Sam. Every light bulb in his room shattered at once, and he laughed when Sam flinched.

"Dean, just…just calm down," Sam said, trying to tamp down his panic and get a handle on the situation.

Faster than he could believe, Dean had him pinned against the wall by his throat.

"Oh, but I am calm, Sammy," the demon murmured as Sam fought to break his iron grip. "And I'm going to very calmly choke the stubborn life out of you so that you can no longer be a colossal pain in my ass."

"Dean, please," Sam choked, unable to comprehend the thought that his brother wanted to kill him. "It's me."

Dean laughed incredulously.

"And what exactly is that supposed to mean to me?" he inquired. "I have no idea why I used to care so much about you, but you're nothing to me now but an annoyance. Like a flea. And guess what, Sammy? I'm the exterminator."

The only thing that saved Sam was the fact that he had been prepared for Crowley. Giving up on reaching Dean or freeing his airway, he pulled the special demon handcuffs from his pockets and snapped them around Dean's wrists. The demon released him in surprise, but he recovered quickly and lunged at Sam. The hunter was prepared this time though, and he held his own. It was a difficult fight, but eventually Sam subdued the demon.

"Honestly, I don't know why you're even trying to do this," Dean tells Sam as the third syringe of blood is emptied into his neck. "You were practically a demon once, you know how this feels. Why are you trying to take that away from me?"

Sam has been doing his best to ignore the demon, but that question draws a short, incredulous laugh from him.

"Seriously?" he asks. "I started the apocalypse, Dean."

"Yeah, so? Didn't you enjoy the rush, Sam, the power?"

Sam meets Dean's eyes, and he can see the genuine curiosity there, along with the hatred and contempt. He sighs, but knows that his brother will remember this conversation when he is cured, and he deserves Sam's answer.

"Yeah, I did," he admits quietly, crossing his arms as he stares down at the demon. "The way I felt when I was running on demon blood, it was incredible. Everything was clearer and I was stronger. I felt like I could do anything, and I liked the sense of control."

"Then why give it up?" Dean asks.

"Because it cost me you," Sam tells him. "And it cost a lot of innocent people their lives. I only ever wanted to rid the world of evil, and when I realized that it was making me evil, I couldn't just keep going."

Dean snorts his contempt, and Sam sighs again.

"Weak," the demon spits.

"Not weak," Sam corrects. "Human."

"Humanity is weakness, Sammy," Dean says, and the nickname sounds so wrong now. "You're just too blind to see it."

"But you've got 20/20 vision?" Sam surmises wearily.

"Yep."

"Good for you," Sam mumbles as he returns to his chair to wait out the hour.

God, he is so tired.

Sam's brain was still struggling to catch up as he hauled a semi-conscious Dean down to the dungeon. He did not understand how this had happened, how Dean could have died and come back so quickly as a demon. Then he remembered seeing the first blade on Dean's bed. He had left it behind, so someone must have brought it to Dean, and Sam had a sneaking suspicion that he knew who that someone was.

Oh well. He would kill Crowley later. For now, he had to figure out what to do about Dean. For lack of any better ideas, Sam chained his brother down in the chair that he had prepared for Crowley, and pulled out his phone to call Cas. He had spoken to the angel on the drive back to the bunker, but neither of them had been all that coherent. Sam did deduce that Cas had beat Metatron though. He wished that he could feel something about that news, but there was no room in his heart for anything but grief at that point.

Cas didn't pick up this time, and Sam's list of people to call for help was officially exhausted. He stared down at Dean, who was fully awake now and practically snarling at him.

As Sam met those depthless black eyes, he knew there was really only one thing for him to do. It was something that he should have done a year ago, and it was a thousand times more important now.

Sam stumbles slightly as he rises to administer the fourth dose of blood, and he wonders if he imagines the flash of concern in Dean's eyes. He decides that he must have, because as he walks over to the demon on legs that are suddenly unsteady, all he is met with is more mockery and contempt.

"You really think that crap is gonna work on me?" the demon asks scornfully as Sam inserts the needle. "Your blood is so tainted, I'm surprised you don't bleed black. It doesn't have a chance of purifying a soul as dark as mine."

Sam cannot help but fear that he is right, but he knows that he has no other choice but to try.

Sam had found the small chapel just a few months after he and Dean moved into the Men of Letters' bunker. He had just been poking around, exploring the maze of hallways and rooms that seemed to go on forever, when he opened a door to find five rows of dusty pews facing a simple altar. It must have been in the small part of the bunker that was above ground, because there was a stained glass window set in one wall that filled the space with multicolored light.

Though it had been years since Sam had prayed with any kind of faith that God cared about him, he had found himself cleaning up the small chapel anyway, dusting off the cedar pews and polishing the large gold cross that guarded the altar before attacking the stained glass with Windex and paper towels. He did not tell Dean about this unexpected sanctuary, knowing that his brother had no use for faith. But though Sam knew that the only heavenly being watching out for him was a busted angel with a screwy head, he would still go to the chapel sometimes and stretch out on one of the pews, breathing in the peace of the space.

It was where Sam had gone when the pain from the trials had gotten too overwhelming, where he had sought refuge when facing Dean's betrayal and Kevin's death. And it was where he went after he had strapped the demon masquerading as his brother to a chair in the middle of a devil's trap. Dean had shouted abuse at Sam as he retreated, and suddenly his little sanctuary did not feel quite so peaceful. But he had not gone there to escape.

He laid the first blade on the altar like some kind of very poor sacrifice, and sank into the first pew. He bowed his head, wondering where to even start with this.

"I guess it's no surprise what I'll be confessing to this time," he said eventually, and his words seemed so quiet, even in the small space.

Despite the fact that it was a church, Sam was not used to praying in there. He rubbed his face with both hands, pressing his palms into his eyes as if he could shut out his problems. But the pain was inside him, and it did not let up. He blew out a heavy breath, and turned his eyes to the cross that he still kept shining.

"I really screwed up this time, huh?" he said softly. "His only crime was not being able to stand losing me, and I pushed him away. I did this to him, by making him feel like all he had left was revenge."

Sam continued to pour out the rest of the hurt and bitterness that had been building over the past several months. He went over all of the what-ifs and the should-have-dones. He recalled that night on the bridge, when Dean had called himself poison and Sam had just let him go. Dean had been wrong that night. He was not the poison, but he had come back poisoned, and by then it had been too late.

Tears were rolling down Sam's face by the end of his confession. As soon as he was finished though, he wiped them away and rose, determined not to fail his brother this one last time.

Sam suffers through another hour of waiting, and Dean's taunts have stopped by the end of it. He cannot even take the time to enjoy the fact that his efforts seem to be working, because he can feel his health deteriorating. His muscles ache as if he has run a marathon, his throat feels like it has been scrubbed with steel wool, and his ears are starting to ring. Dean had been right about the trials; all of the damage that Gadreel and Cas had healed is coming back, and it is hitting him all at once.

Still, he stubbornly gives Dean his fifth injection, and this time the demon says nothing at all. They wait in silence for another hour to pass, and Sam turns his chair back to face Dean. If he is going to go through with this, he wants to be able to see the man that he is saving.

Sam is stunned by how quickly his condition worsens. By the time his watch beeps again, his sleeve is covered with blood that he coughed up and his body is barely cooperating with him. The sixth syringe falls out of his trembling hands as he carries it over to Dean. It shatters, spilling dark blood over the floor of the dungeon. Sam stares at the glistening puddle for a moment, and then closes his eyes. He shakes his head, but then goes back to the table at the side of the room and picks up a fresh syringe, sliding it into his arm.

Dean's green eyes meet his again as he comes back with the new syringe, and Sam is stunned to see that they are glistening with unshed tears.

"Don't do this, Sam," he says quietly, and Sam knows that it is not out of cruelty or self-preservation this time. "Don't do this to yourself for me."

Sam just gives him a tired smile as he slips the needle into Dean's neck, relieved by the evidence that his brother is coming back to him.

"If the situation was reversed, and I was the one damned for eternity," he says softly. "You would do the same for me."

He watches as the words register, and then Dean just closes his eyes. Sam leaves him to his thoughts and returns to his chair, as it is no longer an option to remain standing.

He contemplates the fact that his life will be over in two hours. He finds that he does not mind all that much. He was ready to die after his last botched attempt at the third trial, and the months of loss and heartache have not done much to endear him to life. And if there was ever a good way for him to go, saving his brother and hopefully sealing hell is it.

He does regret what his death will do to Dean though. He knows that once his brother's humanity is fully restored, Dean will be in agony over Sam's loss. Sam just hopes that he will channel that pain into something useful, like helping Cas repair the damage that Metatron has wrought.

He can barely stand when it is time for the seventh injection, so he uses his chair like a cane, dragging it with him to Dean's side and collapsing into it once he is close enough.

"Sammy, please," Dean says, his desperation visibly growing as he takes stock of his brother's condition. "You're going to kill yourself."

"I know," Sam tells him gently as he finds a clear patch of skin to insert the needle. "You're worth it."

"No, I'm not," Dean insists. "Sam, you know I can't let you die for me. What about my perfect ending?"

Sam smiles sadly as he remembers Dean's words from so long ago, at the very beginning of the trials. He thinks about that long and happy life that his brother wanted for him, and he knows that he could have had it. He also knows that he wouldn't have enjoyed a moment of it if Dean's soul had been the cost.

"You get to live it for yourself," Sam tells his brother as he pockets the now empty syringe. "You get to live in a world free of demons, free of hell's curse. I've done so much damage, Dean, so damn much. Let me do this; let me save the world that I've been fighting for my whole life. Let me save you."

They are both crying by the time he stops talking. Dean's watery eyes hold a storm of different emotions, but Sam knows somehow that his brother will not try to stop him this time. He leans over to rest his head on Dean's shoulder. He can feel tears dripping into his hair, but he does not mind. They are the proof that he is finally fixing everything that he let fall apart.

"Why does it always have to be us, Sammy?" Dean asks as Sam's last hour of life ticks by. "Why are we always the ones who have to sacrifice everything?"

Sam sighs, but does not move. Shivers are racking his body, and Dean is an excellent source of both warmth and comfort.

"Maybe it's because we're the only ones who can handle it," he answers eventually, his voice slurred.

"I cannot handle this," Dean tells him, and now his body is shaking too.

"Yes you can," Sam says, and with a sudden surge of energy, he manages to sit up, meeting his brother's gaze. "We were always gonna die young, Dean, we both knew that. I know you wanted me to outlive you, but since when has life worked out the way you want? My number has been up for years, and I'm okay with it. What I wasn't okay with was the idea that I might not get to spend eternity with you. We already know that we share a heaven, and there was no way that I was letting you miss out on that."

"Heaven is closed for business, Sam," Dean chokes. "You're just gonna get stuck, like Kevin."

"Then make that your mission, Dean," Sam says, gripping his brother's arm. "Cas took care of Metatron, did I tell you that? He won, and he can start fixing things. He's gonna need your help, so give it to him. I'm closing hell; opening heaven can be your job."

Silence falls between them again and Sam rests against Dean once more as his energy flags. He cherishes the sound of his brother's heartbeat, strong and loud in his ear, even though his breathing is slightly uneven. Dean flinches when the watch alarm beeps at last, but Sam just sighs in resignation and sits up.

"I'm sorry, Sammy," Dean says as he watches Sam pull the syringe from his pocket and press it to his arm. "For all of it."

"I'm not," Sam tells him, meeting his pained gaze. "I never got to tell you, but I'm proud of us too. We're closing hell, big brother, you and me together. We did good, Dean, and you get to do more good after this."

The syringe is full now, and Sam pulls it from his arm. He uses his free hand to unlock the shackles on Dean's wrists, knowing that he will not try to stop Sam now, no matter how much he might want to.

Sam's hand shakes, so Dean takes it and guides it up to his neck, helping his brother push the plunger that sends the last dose of blood coursing into his system. They both sigh, and Sam gratefully tosses the used syringe away. His arms have started glowing without him noticing, and he takes comfort in the knowledge that he really is still completing the trials.

He slices into his palm with Ruby's knife, and though he sees Dean wince, his brother still does not try to stop him, and for that he is grateful. He carefully says the words to the spell that he memorized a year ago, the one that would fully restore Dean's humanity and lock the gates of hell forever. He meets Dean's eyes, and though there is endless pain and grief in them, they shine with pride and humanity, and they warm Sam's trembling body. As he finishes the final words of the spell, he knows that there is one more thing left to say.

"I love you, Dean," he tells his brother.

Dean manages to smile and let out a sob at the same time, and Sam finds himself wrapped in a tight hug. He closes his eyes, relishing this final embrace.

"I love you too, Sammy," Dean whispers in his ear. "I'll see you upstairs, okay?"

"Better not be too soon," Sam warns him as he forces himself to pull away. "I want a couple decades of peace and quiet before you get there."

Dean laughs, and Sam knows that this is the last image he wants to have of his brother. He places his bleeding hand over Dean's smiling lips, and it is all over in a blinding flash.

A/N: Thanks for reading! For those of you who follow my other stories, know that I am still working hard on them; I am just taking a break with this one. I hope you liked it, and I would love to hear your thoughts.