AN: Wanted to get this up before the new episode airs tonight, even if ya'll don't get a chance to read it until later. I based this off of the promo for tonight's episode, "Southern Comfort," and a few of the lines were lifted directly from that. This is my head-canon explanation for why Sam left Dean in Purgatory. While I know the episode would never play out like this exactly, I feel like it's the best explanation for Sam's behavior. Hope you guys like it. Happy Winchester Wednesday! :)

You Left Me

As Sam shakes Benny's hand, Dean can see a mixture of confusion and outrage on his face. The tension between the two brothers is palpable. Benny must notice it too, because he frowns as he pulls his hand away from Sam's.

"Well, I'll be on my way then." He turns toward Dean, and Dean thinks he's gotta be pretty brave to be turning his back on Sam. Benny smiles at him, embraces him quickly, and pulls away. "Thank you, brother. If you ever need anything..."

Dean nods and smiles back. "I will."

And with that, Benny's gone.

Dean's not sure how long he and Sam stand on that pier, in the dark and the cold. It could be seconds, or minutes, or an hour.

Finally, Sam breaks the silence.

"A vampire, Dean? After everything we've been through? After what happened with Ruby?"

"This is different, Sam."

"How? You're trusting a monster, just the same as I was, and look where that got me." He steps closer to Dean.

"Sam-"

"And what about Amy? You told me she was a monster, and she would kill again. You went behind my back – lied to me – and you killed her. How is this any different?"

"Sam-"

But now that Sam's got started, he can't stop. He's practically in Dean's face.

"You're a hypocrite, Dean. That's what you are. You-"

"Sam! Shut up!" Dean screams it, and Sam shuts his mouth so fast it's slmost comical.

Dean takes a step back from his brother.

"You don't have all the facts, Sam. You have no idea what I went through in Purgatory. None. You can't possibly. Benny saved my life. More than once."

"Like Amy did for me?" Sam retorts.

"I'm not finished." Dean's voice leaves no room for argument, and Sam crosses his arms over his chest in childish protest. "He found the way out, Sam. He got me out of Purgatory. Which is more than I can say for you."

"Dean-"

"You never even wanted this life, Sam. And I get it, whatever. But to just give up? Not even attempt to find me? I was gone, Sam. Stuck, in Purgatory, for a year, and you never looked for me. You gave up on the job, you gave up on Kevin…you gave up on me."

"Dean-"

Tears are beginning to form in Sam's eyes, but Dean doesn't even notice. Sam wouldn't let him talk before? Well, now it's his turn.

"And then you turned to some girl," Dean continues harshly.

"Her name's Amelia."

"You gave up on your own brother for a girl and a dog. For college and some apple pie life."

"Dean, please-"

"You left me to die for a girl?!"

And that's when Sam explodes.

"No! I left you to die because I couldn't do it anymore, Dean! I couldn't, man. You were gone, I had no idea where you were, if you were even alive. And I couldn't do it anymore."

The words are flowing out, unstoppable.

"I gave up, Dean. Something in me just kind of…broke. And I couldn't…I couldn't do anything to fix it. I'm sorry, man. You have no idea how sorry I am. Dean, I…"

He trails off, bites his lip, and looks down.

Dean feels his heart hit the floor.

Well, shit.

What the hell can he possibly say to that?

Eventually, Sam looks back up at him. "I didn't move on. I never really moved on. I just kind of…I fell apart. I almost…"

Dean can see where Sam is going with this and he hates it. He doesn't know what to say. All he can come out with is his brother's name.

"Sammy..."

"I wanted to end it. I was going to end it. This night I was on the road, just driving. That's all I did for the longest time. I was just driving and then all of a sudden my foot was touching the floor and I was doing a hundred, tearing down the road, heading toward I don't even know where. I knew what I was doing. I just wanted it to be over. But then I hit something hard. I went back and found this dog lying on the side of the road. It was still alive, but barely. He got lucky, I must have only clipped him."

Sam pauses, and when he continues his voice is trembling slightly.

"That dog saved me, Dean. Suddenly it was my fault, again, that someone was hurt because of me. That someone's life was ruined. That someone was in pain. I couldn't lose that dog, too. I couldn't lose anyone else. I had to save him. He had to be okay, I had to make sure of it. He…he had to be okay."

Sam turns away from his brother, and Dean can see him trying to discreetly wipe the tears away.

"That dog saved me. He gave me a reason to...I had to be there for him because he needed me. Turns out I needed him, too."

Sam turns back to Dean and keeps going.

"And then I meet Amelia. She helped me out during a bad time, Dean. I started living a normal life. Got a job, moved in with her, gave my dog a name. Applied to colleges. I never felt like I was giving up hunting. I just…I just couldn't be in that life anymore, Dean. Not without…not without you."

Sam stops talking and tries to pull himself together. Dean watches the tears fill his eyes again.

"So I tried to move on. But even now it all still seems like a lie, because I was never really okay, Dean. I still slept with a knife under my mattress. I still had nightmares every night. I still wore this around my neck everyday."

He reaches into his pocket, and there it is: the amulet Dean threw away three years ago when God became just another father figure to disappoint him.

"You…you went back for it?" Dean asks quietly.

"Of course I did. I've had it ever since. Except for that one year. That year I…the year you lived without me. All that time it was in the glovebox of the Impala. I stashed it there right before I said 'yes' to Lucifer. When I finally got my soul back, I took it out of the car. It's been with me ever since."

"Sammy…I…I didn't know."

Sam nods. "I wanted to help you, Dean. I really did. But I just didn't know what to do. I couldn't help you when I couldn't even help myself. I did leave you there to die, Dean. And I'm sorry. But I only…I only did it because you were the one who was gone, but it felt like I was the one who was dead."

Dean doesn't know what to do, doesn't know what to say. He'd just assumed that Sam had decided he could live without him. But it turns out that Sam had finally decided that he couldn't live without him.

"I'm sorry, Dean. I'm sorry."

"Sammy…" The word is torn from his lips in a hoarse whisper.

"I'm so sorry," Sam says again.

Sam's sobbing now, tears falling down his face, shoulders shaking.

Dean crosses the space between them and pulls Sam to him, wraps his arms around him tightly. The amulet falls out of Sam's hands and hits the ground softly.

"It's okay," Dean whispers.

"No, no it's not, Dean." Sam's shaking his head against Dean's shoulder, his tears soaking Dean's shirt. "You can't forgive me for this. I've let you down. I've always let you down. I-"

"Sammy, stop. You're annoying as hell, but you're still my brother. It's going to be okay."

He hugs Sam tighter, not telling, but showing him that he forgives him. Because what else could he possibly do?

"We're family," he says quietly.

"Dean…"

It sits there between them. It doesn't need to be said. They both already know it.

But then Sam says it anyway.

"I missed you."

And Dean replies, "I missed you, too."

...the end...