Looking out from his own eyes is the only thing that feels familiar to Dean Winchester. His body is a stranger, powerful and strong, it feels nothing but a coursing desire for destruction. He walks and moves but feels little that reminds him of the person he used to be. He doesn't feel hunger or fatigue, hasn't for a long time. Instead, he feels an insatiable desire to use the power in his limbs, his mind, his heart, to kill.

Crowley went down first. That felt particularly satisfying. His dark suit perfectly in place, his eyes unimpressed when Dean held up the First Blade. "What, you're thinking to use that pig-sticker on me? The King of Hell and your only remaining family?"

Dean stepped closer. "You aren't my family. I don't have any more family."

The actual killing is pretty anticlimactic. Dean presses the blade into Crowley's chest. Crowley looks into his eyes, confused. Dean pulls it out, swings hard at the base of the demon's neck and watches his bearded head roll away from its falling corpse.

Later, he takes care of Castiel. Dean is fairly sure the angel is dead, but his body had blinked out after Dean drove the Angel Blade through his chest, so he couldn't be sure. Cas hadn't looked confused. He'd looked…sad. Disappointed? It was hard for Dean to read emotions now. Either way, he's gone.

Now, there is only a driving need to find Sam. He guesses that Sam will be the easiest to kill. He's only human, after all. He has no real weapons to fight the kind of power Dean has now. A power that simmers under his skin and races faster and faster with every passing day. There isn't any part of Dean left that thinks killing Sam is a bad idea. The "brother" in him thinks he is doing Sam a favor. He'll make it fast. He won't make the kid suffer. He just…Sam has to go. He's the only loose end, the only thing tethering him to his earlier life. Everyone else is already gone. With Sam out of the picture, Dean will be free. He can unleash his power on the world without worrying about anyone wanting him to hold it back.

The problem? Sam is proving damned hard to find.

The little wooden house smells like sulfur. Built ten feet off the ground on square wooden stilts, it has three rooms and a porch with a rickety staircase to the dirt path below. This is probably the first time in Sam's memory that this smell can be traced to nature and not a demon. Holed up in the muddy swamp of Pawnee, Louisiana, Sam is finally ready for Dean. Bugs and birds and other creatures he he's too tired to think about keep up a steady racket outside the screened windows. The simple fact that they're noisy in going about their business lets him know that Dean hasn't found him. But, he's ready now.

His own blood, check.

Dean's blood. Check.

A knife coated in both. Check.

The spell Rowena translated. Check.

Practicing the words over and over, he's memorized them. When he's toe to toe with Dean he can't lose them and fail. Not Again. This time, Sam is going to save him or die trying.

It's time to let Dean know where he is.

Dean's phone buzzes in his pocket. The thing hasn't rung in weeks. It surprises him. When he looks at the screen, he's further surprised. Maybe this won't be so hard after all. "Sam."

"Yeah."

"You ready to talk?"

There's a long pause. "Yeah. Yeah, Dean, let's 'talk.'"

There's something there. Sam thinks he knows something. Probably is going to make a long, tiring pitch about Dean continuing to fight the Mark. He doesn't know that Dean's already settled that dilemma. "Where are you?"

"Louisiana. You?"

"Text your coordinates. I'll find you."

Another pause. A tired sigh. "Yeah, I know you will."

It's two days later when the insects and animals fall silent. It's about nine o'clock at night, and Sam hasn't really slept in a week or more. This is his one shot, he's well aware. Charlie died to give him this shot. If he fails, Dean's killing him will be a favor.

He hears booted feet coming up the outside stairs, pulls in a couple of deep breaths to try and calm himself down. He can feel his heart pounding. He stands by the fireplace, the knife in a sheath at his side. The spell is written down in his pocket, but he's got it down by now. The next ten minutes will decide the rest of his life, or end his life. Or, both. The screen door creaks and the rusty knob on the door turns.

The door swings open. It's Dean, of course.

The first thing Sam notices are his dead eyes. If there's anything that's sets him on his course of remove the mark or die, it's that dead look in Dean's eyes. Dean Winchester is a cauldron of emotion from head to toe. Always has been. Even when he's trying to be stoic, Sam can see everything he's feeling in his eyes. This guy watches Sam with nothing but cold anticipation.

Sam settles. "Hey, Dean."

"Sammy. Nice place you've got here."

Sam shrugs. "So, what are you doing here?"

Dean smiles a reptilian smile. "Oh, come on, little brother. You must know."

Sam nods. "I just want you to say it. In case I'm wrong."

Shaking his head slowly, Dean comes closer. "You're not wrong."

"Then say it."

Dean's arms are loose at his sides. His hands curl into fists. "Well, Sammy. I'm here to end you."

Sam nods. "And why is that?"

"What?"

Sam feels the hilt of the knife that rests on his hip. He's ready. "Why do you want to end me?"

"Because I do."

"Uh huh. You want to kill me, but you're not sure why?"

"The fact that I want to – and I really do want to – is all the reason I need."

"So, if I tell you this will be the last step, that this will be what turns you full on into an immortal murderer, that doesn't matter anymore, does it?"

Dean shakes his head 'no', slowly, his eyes never leaving Sam. "What matters is that I get you out of the way and get on with things."

"Get on with killing things."

"Yes, Sam. Killing things. What, you think I don't know? You think hearing myself say this stuff will somehow make it clear to me that I have finally become the killing machine I fought so hard against becoming? Fine. I'll say it plain. I'm a killer. I'm the best goddamned killer out there. And, it's gonna be a wild ride just finding-"

Sam strikes. He grabs Dean's right hand, slices through the mark with his blood-dipped blade and starts saying the words to Rowena's spell. He translated enough to know that it calls for using murdered brother's blood (which, how weird that he and Dean have both been murdered) to over-power the "murdered brother's blood of Abel," which is what was used to create the Mark of Cain.

Dean isn't about to just stand there and let Sam "Latinate," as he used to say. He swings at Sam with his left fist and Sam flies across the room. He hits the wall and fights to stay conscious. He's done the only physical thing he needed to do to remove the mark. Now, it's a matter of staying conscious long enough to get all the words of the spell out while Dean beats on him.

He feels blood in his ear and can't hear out of that side. He keeps his focus through sheer willpower. Miraculously, he remembers the words and continues with the spell.

He'll never forget the look of menace and hatred that Dean is wearing when he stomps across the room to pick Sam off the floor. His face looks like one of the hundreds of monsters who'd come after Sam his whole life. It helps him feel less bad about pulling the lead-filled truncheon out of the back of his jeans and swinging it at Dean's head. He knows Dean will block it, but the weighted wood might still crack an arm or something.

Dean grimaces when Sam connects, but Sam can't tell if it's from pain or from anger. He pulls Sam up by his shirt. Sam can feel it tightening around his throat. He keeps talking. Only two more lines to go. He doesn't ask Dean to stop, doesn't plead for his brother to come back. He just looks Dean in the eye and remembers everything he ever loved about his brother. It stays Dean's hand for maybe five seconds. But, it's enough. Sam finishes just as Dean delivers what Sam's sure will be a death blow to his head. The punch connects just as the last syllable leaves Sam's mouth.

Dean is gripping Sam's blue and black checkered flannel shirt in his hand when he feels a heat sear into the cut Sam inflicted on his forearm. He's pretty sure he's broken Sam's neck with his last blow, and is moments away from feeling the dark satisfaction he expects, when the heat becomes intolerable and he lets go of Sam.

His arm throbs and burns, which is surprising since Dean hasn't felt anything close to pain for weeks. He glances down at the mark, expecting it to be bleeding profusely. Instead, the cut Sam inflicted is sealing, and the mark…it's fading.

Dean stares. It's true. The mark is actually growing fainter, like it's being bleached away. The infusion of something like warmth begins to run under his skin. But, it's not the dark, fiery, heat that he's become accustomed to. It's like…it's just warmth. Like a fire flaring to life on a cold night, he begins to warm from the inside out.

His body is weakening, and he drops to his knees. His limbs feel heavy and sore, like they've been overused. The mark is almost gone, like a faint peach-tinted scar. He stares. And, right before his eyes, it disappears all together.

It's gone. The Mark of Cain is gone.

Dean feels the unfamiliar pulling of a smile start. "Sammy, it's, look, it's-"

He holds his arm up to show his brother, but Sam's eyes are closed. His neck is at a funny angle and he's lying on the floor not two feet from where Dean's knees rest on the floor. "Oh, no. Oh, come on. No. Sam. NO!"

He shuffles closer, puts his hand on Sam's neck, knows in that moment what he's done to Sam. And, what Sam's done for him. And it's impossible to process.

It's probably been hours that Dean has just sat here on the floor holding Sam's corpse against his chest. He gets it. He really does. That Sam was willing to do this for him. He would have done the same. But, Dean can't get past what he's done to his brother. "You stupid son of bitch." He closes his eyes and can't think what to do. Sitting here, holding Sam and knowing the cost of saving him, he doesn't think he can live it.

He makes the decision to join Sam and immediately feels relief. Yes. Both of them will end here. The mark is gone and now they can go out together. It makes sense. He'll burn the cabin. Their bones will go up in smoke, there'll be nothing to attach them here. It's the closest to a hunter's funeral he can give them.

"Sammy, I've got do a few things, but I'll be with you in a minute, okay?" He gently leans Sam away from him, sets him slowly down on the floor and stands up. Every joint protests. His body is so fatigued, he has to lean both hands on the table to wait for his vision to clear. And there, on the stained wooden surface, is a letter with is name on it.

He doesn't want to read it. He doesn't want to hear Sam's last words to him. He just wants to join him and be done with his whole retched existence.

But, of course, he opens it.

Dean,

If you're reading this, I'm dead. Ha. I've always wanted to write that. It's so Agatha Christie. Anyway, please, please tell me I got the spell out before you killed me. God, if I failed in that, then, I don't know, I'm glad you killed me, I guess. If I did it right, then I want to pull a Private Ryan on you and tell you that to me, this sacrifice was worth it. You've earned it. I know a big part of you will not want to go on, you'll feel like giving up because you killed me. But, I don't look at like that. The Mark killed me, not you. And, if I finally did it right and actually saved you? Then that's a death I can be proud of. You've sacrificed everything for me, time and time and time again. And, if this sacrifice actually got rid of that damn thing on your arm, then I'm happy. Seriously. I'm ecstatic. We know this life sometimes requires everything. So I'm going to ask you to go on fighting for both of us. Don't give up. You're too important. You're a force for good in a world that needs you. Please don't make that mean nothing. I always looked up to you, I always tried to be like you, and, if I'm dead and the mark is gone, then I finally succeeded in DWDWD. (Doing What Dean Would Do.) It's what I've tried to do my whole life. So, don't think of this as a loss. Think of this as a win for Team Winchester.

Okay, this is getting long (there's not much to do in this damn cabin while I wait for you) but the gist is, don't beat yourself up over this. Go on living, go on fighting. I'll be right by your side until I see you on the other side. And, by now, you know it, but I'll say it anyway - Love you.

Sam.

He shouldn't have read it. Dammit. "Damn you, Sammy. Don't ask this of me. Don't ask me to live with this." He looks down at Sam, wipes the tears out of his eyes. "Always a day late with us, isn't it? Jesus. Couldn't you have finished the damned spell before I broke your fucking neck?" He looks around, sees Sam's bag in the corner. There should be some accelerant in there. "Sorry, bro, but you can take your 'don't give up' and shove it straight up your dead ass. I am not sticking around here without you. Not when you died by my own fucking hand!" He finds the small can of gas and unscrews the top. "I can take a lot. I can take that I murdered Crowley. Hell, he deserved it for the hundreds of year' worth of shit he pulled on people. But, Cas? You? No. Not gonna happen." Dean spills the gas around the wooden floor, on the walls, even on the table. But he pockets Sam's letter, and he doesn't let any of the fluid actually touch his brother. Dean pulls the book of matches out of its zippered pocket. He should start the fire then eat the bullet, he thinks. That makes sense.

He strikes the match and feels a sharp wind behind him, blowing the match out. A low, tired voice says, "Dean. This isn't the way."

Spinning, Dean sees Castiel standing there, like Dean didn't run him through with his own Angel Blade three days ago. "Cas? How the hell are you alive?" Dean is relieved to see his friend, feels a burden fall off his heart that he didn't actually kill him. But that's quickly followed by annoyance that the angel showed up at this particular moment. If Cas susses out what Dean intends, he'll stop him.

Castiel sighs, looks around the cabin. "I manufactured a blade that was simple chrome, and not a genuine Angel Blade. The lowest Cherub would have known the difference, but to humans it looks much the same." He sees Sam slumped against the floor. "What happened here?"

Dean closes his eyes. "I think it's pretty clear what happened."

Cas steps to him, holds up his right arm. "The Mark is gone." He looks at Sam. "The spell worked."

Dean looks at him. "You knew there was a spell?"

Cas nods. "I knew Rowena said there should be a spell. I knew Charlie sent the codex translation right before she died. I know Sam said he was going to save you."

He walks to Sam. Dean watches him put his hand on Sam's chest. "Yeah. He saved me. And I killed him."

Castiel looks up. "Not you. The Mark."

"Which I was wearing. So."

Cas's nose twitches. "Is that gasoline?"

Dean doesn't answer.

Cas shakes his head like he's disappointed in Dean. Then, he reaches both hands out to Sam, puts them around his neck and Dean feels a wave of power go through the room. Sam takes a breath, turns his head, eyes still closed, and pulls his legs closer to his body.

Dean's whole body feels like it's been filled with light. "Cas?"

Cas smiles. "Dean, I am an Angel of the Lord after all."

Dean is next to Sam on the floor in two seconds. "Sam? Hey, you in there?"

Sam turns toward his voice, opens his eyes. He looks at Dean, then to Cas. Then, to Dean again. "What'd I miss?"

Dean laughs. He can't help the tear that rolls down his cheek. "You saved me, I killed you, Cas to the rescue. Same old. How do you feel? You okay?"

"I what? You -" He seems to get clearer with the next blink. "Wait. I saved you…it worked?!" He tries to sit up and grabs for Dean's arm. Dean grasps his hand in return, pulls Sam into a sitting position, puts a hand behind his back to steady him.

Sam only has eyes for Dean's right arm. "It's gone? It's really, truly, gone?" He rubs over the spot where the mark stood for the last year and a half. He looks up at Dean, wonder on his face. "It's gone?"

Dean nods. "Yeah, Sammy. You did it. It's gone."

Sam smiles, his dimples popping into his cheeks. "Thank fuck," and he throws his arms around Dean's neck. It pulls Dean off balance and they fall to the floor, but Sam doesn't let go. Dean can't breathe very well, but he grasps Sam just as hard.

Finally Sam lets go and reaches a hand out to Cas. "Cas…"

Castiel takes Sam's hand and pulls him back up so he's seated on the floor. He doesn't let go of Sam's hand. Then, Sam pulls Castiel into a hug, and they're all tangled up together on the floor, the smell of gasoline forgotten in their first moment of true happiness in what feels like years.

Later they will remember Charlie. They will remind Dean that it was the mark that killed all those people, just like when Sam was possessed, or when he had demon blood, or when he was soulless. And Dean will get a little less tight around the eyes, because if anyone can understand doing something you have no control over, it's his brother. The three of them will go back to the bunker. They will sleep (well, two of them will sleep) and then they will begin to put their lives back on track. To look for people to save. To rejoin the family business.

The End.