Disclaimer: Not mine.

Author's Note: So remember that time I said I was done writing fixit? Yeah, it turns out I have zero willpower. Who'd've guessed?

I owe Cheryl thanks twice over – for betaing this and for not letting relegate it to the "Random Unpublished Stories" folder on my hard drive.

Summary: The Mark of Cain has a price, and it's not what Dean's expecting. But it may just be the thing to break through Winchester stubbornness.

Resolution

"We're here," Dean says, and maybe he sounds a little petulant, but this is starting to get on his nerves. He's devoting all his patience and self-control to not pushing Sam before he's ready, and he has absolutely none left to waste on the demon who's grinning at him like she's in on some secret Dean doesn't know. "So give me the damn knife. Crowley said you found it."

"We found it all right," the demon agrees. "But we couldn't pick it up. You have the Mark of Cain."

"I need to be the one to pick it up? But it's at the bottom of the ocean."

"You don't have to go there physically. There's simply a… a quest you have to complete, and the Firstblade will come to you."

Dean can sense Sam rolling his eyes.

"Of course there's a quest," his brother mutters. "What is it this time? Kill a demon? Bring back someone from the dead?"

The demon scoffs, and Dean hefts the knife in his hand. He is so ready to plunge it right into her that he almost hopes she'll give him an excuse.

She must sense that, because she backs away.

"You know, I always thought you Winchesters would be smarter," she says. "With that reputation you've got. Even the boss respects you. Sometimes. Why do you think he didn't tell you all this himself? Because he was scared of what you'd do to him. If you even believed him in the first place."

"Sweetheart," Dean drawls, fingers tightening around the handle, "believe me, you don't want to lie to me. You want me to carve the answer out of you, I will. But it'll be easier for all of us if you just tell me."

She pouts. "Fine. Be like that. The only way to get the Firstblade, the weapon of Cain, is to be worthy."

"Yeah, we've been through that. Cain tested me against a bunch of demons –"

"You think it's about your physical strength? Abaddon's a Knight of Hell, and she's stronger than any ten demons you'll ever meet." She walks up to them, stands between them and pokes Dean in the chest with one finger. "You have to prove you're mentally, emotionally ready to be a killer, Dean."

"I can kill you right now and prove it."

"Sure you can. That's not the point."

Sam stiffens, like he's just realized something. Dean's eyes flick up to his, but Sam's not looking at him. His gaze is on the demon and his face is unreadable.

"It's very simple," the demon goes on, taking a step away from Dean, towards Sam, and suddenly all Dean's instincts are screaming a warning. "Prove you're a killer worthy of Cain's inheritance."

When she moves, it's too quick for either of them to react. She's behind Sam, and she's pulled one of his arms behind his back and twisted it, forcing him down to his knees. Her other hand is at Sam's throat, red nails digging into the delicate skin by his jugular vein, and Dean doesn't dare move, doesn't dare breathe –

And Sam looks sort of sad and resigned, and he's not even trying to get away from her. If someone doesn't start explaining things quickly, Dean's going to kill the demon bitch, Firstblade be damned.

"Go on," the demon whispers, smiling at him. "Go on, Dean Winchester. Prove you're a worthy successor to Cain."

She tilts Sam's head up, exposing his throat, and Sam lets her, and realization and understanding come to Dean in a flash, followed a moment later by white-hot anger.

"Get out," he snarls at the demon. "Now, before I decide to carve the name of God into your ribs."

"Suit yourself. But you'll have to do it if you want the weapon."

The demon goes, and Dean grabs Sam, hauls him upright and gives him a hard shove in the direction of the Impala.

"Dean," Sam begins, in that tone of voice that means he intends to launch into a long and detailed explanation, and Dean is done.

"Shut up," Dean snaps. "Shut up and get in the car, and I don't want to hear another word from you till we're back in the bunker."

"But –"

"Go."

Sam goes. Dean gets in the driver's side and shuts the door hard enough to make Sam wince, and feels savage pleasure at the reaction. He pulls out his phone and dials Crowley.

As expected, the call goes to voicemail.

"Son of a bitch," Dean growls into the phone, "try a stunt like that again and I will feed you to your own Hellhounds. Call me, and when you do you'd better have figured out a way to get the knife that doesn't involve Sam."

He drops the phone on the seat and drives. It's dead silent, neither of them speaking, and Dean's relieved. If Sam says anything right now, Dean's going to pull over and deck him.

It isn't until they're back in the bunker with the library table between them that Dean says, "Please tell me you didn't know what she was going to say before we went there."

"I didn't know," Sam says. "I just… wasn't surprised. You said Cain told you there'd be a price, Dean. And it's a demon weapon. It was bound to be something difficult."

"Yeah, like killing Hellhounds difficult or curing a demon difficult. Not…" Dean swallowed. "Not that."

"What choice do we have?"

Sam sounds reasonable and matter-of-fact, and Dean suddenly remembers how willingly he let the demon pull up his chin to bare his neck for Dean's knife.

"You think I'm actually considering this." It isn't a question.

"You want to gank Abaddon –"

"Sam!" Dean goes around the table and grabs Sam's arms, forcing him to stay still and look Dean in the eye. "I want a straight answer. Do you think I'm seriously considering killing you to get a magic knife?"

Sam doesn't say anything, and that's answer enough.

Dean pulls away, feeling suddenly sick. Sure they've had their differences, but he never even imagined Sam would think –

"Just…" His voice trails off. He clears his throat and tries again. "Explain it to me, Sam. When I went to all that trouble to save you once, when I gave up on closing the Hell gates and let Crowley walk, when I sent an APB out to all Angels, when I did something that made you so mad you barely even talk to me anymore, all to save your life, why would I throw it all away for a knife?"

Sam won't meet his eyes.

"Oh. Right." Dean shakes his head. "Stupid me. I wasn't saving you for you. I was saving you for me." He really wants to walk away, to shut himself in his room and take some time to regroup, but not talking about things hasn't really worked out for them in the past, so he pushes Sam into a chair. "Why would you think that?"

Sam shrugs. "You haven't thought of me as your brother for years, Dean. You said so."

Dean blinks. "I've said a lot of crap, but when did I ever say I didn't think of you as my brother?"

"You said Benny was a better brother –"

"And I was frustrated and didn't mean it and you know that perfectly well. You want an apology? I'm sorry. I was a jerk. There. But I know you, Sam, that's not it. Tell me the truth. You said yourself secrets ruin relationships."

Sam turns away from him. "You know what you said, Dean, and I'm done playing this game."

"I don't know! Sure I was an ass to you about Benny, but then I killed him to get you out of Purgatory, so you can't hold that against me. What did I say to make you think I would be willing to kill you?"

Sam shakes his head, getting to his feet, and Dean's heart sinks. He thought their relationship meant enough to Sam that he'd at least be willing to try –

"Sammy, please."

It's outright begging, and he never begs, but this is the last argument he's got. It's also the one that makes Sam pause in the doorway and turn to him.

Dean would laugh if he weren't so desperate. Little bleeding-heart Sammy never could resist pleading. Dean knew he was under there somewhere.

"Sammy."

"I can't keep doing this," Sammy says.

Dean nods. "I know. We're not going to keep doing this. I swear to you, Sam, I really don't know what you're talking about. Just… tell me." Sam hesitates. "C'mon, Sammy, what happened to your sense of fairness? You owe me this." Sam scowls. "Sammy. Look, I don't know what I said or did, but whatever it is, I'm your big brother and I've been watching out for you all your life. And I might've screwed it up sometimes, but I think I still deserve the benefit of the doubt."

Sam sighs, dropping into the chair next to Dean. "The voicemail."

That's all he says, like that's supposed to mean something, and Dean bumps his shoulder lightly. "Which voicemail?"

"The voicemail. The one before… before Lilith."

Dean racks his mind. He did leave Sam a voicemail then, and he doesn't remember exactly what it was but it was something sappy and girly. It clearly wasn't sappy enough, because Sam went after Lilith anyway, but he never imagined it was so bad that Sam would still be upset about it years later.

"What was so terrible about it?" he asks, honestly bewildered.

The look Sam gives him is hurt, like he thinks Dean's deliberately messing with him.

"Sam?" Dean prods. "If I knew, I wouldn't be asking."

"You said I wasn't your brother. I was a monster and you were done trying to save me."

"I… what?" Oh, no. Sam's got something really mixed up, because Dean never sent a voicemail like that. He couldn't have. Ever. No matter how mad he was. "Sam, no."

"I think I know what I heard, Dean," Sam snaps, getting to his feet. "We're done here."

"Sam!" Dean's on his feet too. "I'm not lying to you. Look at me." He pulls Sam around. "Look at me. I am not lying to you. I never said you're not my brother, and if anyone calls you a monster I'll kick their ass."

"But I heard –"

"I left you a voicemail." Dean keeps his grip tight, not risking Sam walking away. "But that wasn't it."

"What was it?"

"I said you were my brother and we could fix things. You're my brother, Sam. You'll always be my brother, and we can always fix things. There's never going to be anything so bad we can't fix it."

"But I heard you," Sam says, and he sounds lost and bewildered and Dean wants to comfort him, but Sam needs to ask for it.

"I don't know what happened," he says quietly. "Why would I lie, Sammy?"

Sam stares, and Dean sees the moment when Sam believes him, the moment when the last of the mistrust fades from Sam's eyes and there's just Dean's baby brother, vulnerable and unguarded.

"Dean?"

"Yeah, Sammy."

"You didn't say you were done trying to save me?"

"I will never be done trying to save you."

"Dean."

Dean's not expecting two hundred pounds of hunter to slam into him, so he staggers under the weight for a moment before he catches himself and wraps both arms around Sam.

Sam's saying something, jumbled apologies and promises and descriptions of the voicemail he heard, and Dean rubs his back.

"It's OK, kiddo, calm down."

"I went after Lilith because I thought –"

"Hey," Dean snaps. "We're done being guilty about Lilith."

"But I should've known you'd never say –"

"And I should've known that if you'd heard my actual message you would've waited to talk to me. We were both idiots." Dean runs his hand up into Sam's hair. "So that's why you thought I didn't save you for you?"

"I'm sorry."

"I'm sorry, too. You would never have believed that voicemail was real if I hadn't given you plenty of reason."

Dean feels Sam's hands fist his shirt, and they really should be sitting down if Sam's going to expect Dean to support his full weight. He doesn't move them, though, because this is easy and comfortable and familiar, and right now they both need something familiar.

"So are we brothers again?" Dean asks. He already knows the answer, but he needs to hear Sam say it.

Sam nods frantically against his shoulder. "Yes, yes, I'm sorry, I should never have said –"

"Hey, shh, it's OK. I get it. You were pissed, and you had a right to be."

"You let him possess me," Sam says, not accusing this time, just explaining. "Lucifer possessed me, Dean. Meg possessed me. Azazel put his blood in me against my will. I can't – Dean, you have to understand. They took everything that made me me, and free will is all I have left."

"I know. I'm sorry I had to do it, but… I'm not sorry you're alive. And I can't promise I won't do it again. If it's your life on the line… I will do anything I have to do to protect you."

Dean rubs Sam's back, hoping that's not going to be a dealbreaker.

"I know. It's… Well, I'd rather you didn't do it again, but I guess I can live with it. Goes with the territory of overprotective big brother, I guess."

Dean laughs. "Damn straight."

"Just… Promise me you won't do it except as an absolute last resort."

"I can do that. Sam, there is nothing, other than saving your life, that matters enough to me that I'd pay the price of letting something possess you. OK?"

Sam pulls out of Dean's arms, meeting his eyes and then looking away with scarlet cheeks.

"Well… You can do it if it's your life on the line, too. You know. If… If it's ever the last resort."

And that, right there, is why Dean loves his baby brother more than anything else in the entire world.

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