5x04, The End. Future Dean informs Present Dean that Sam did not, in fact, die in Detroit; he said yes. Yes to Lucifer. Dean can't understand what would compel Sam to do what he'd sworn he never would, and asks "Why would he do that?"
I'm going to fill in a few missing pieces. This is my take on why and how Sam said yes to Lucifer in 2014.
This fic got quite a lot darker than I initially intended it to, but I hope I got the depths of Sam's despair across, because we know that he wouldn't have taken the decision to say yes lightly. Issues of depression and a bit of alcoholism, so read no further if that bothers you.
Poems used (in bold): Richard Siken's "Road Music" and "Scheherazade"
November 18th, 2014.
Sam swallowed the whiskey and felt the sharp taste hit the back of his throat. Not that he reacted to it. He was used to drinking a lot by now. It is the Winchester way, after all, Sam thought to himself bitterly. Let drink kill you before the monsters do.
Sam slammed the bottle onto the table in front of him, alone in the dilapidated house he was squatting in for the week. Sam had been alone for a while now. He hadn't spoken to his brother in nearly five years – Dean didn't want to know anymore. Sam had pleaded with him, told him he was scared, asked for his help...and Dean just responded that they were better off apart. It had finally dawned on Sam that, in fact, his older brother was repulsed by him. Sam disappointed Dean; disgusted him. Any hope of returning to how they had been before this whole thing exploded had long faded into the past.
The first time Sam had seen these emotions emerging from Dean was about seven years ago, when he first found out that Sam was using his powers given to him by Azazel. Dean had been so furious that he'd gone behind his back, had been working with Ruby...that he was beginning to look at his younger brother and not recognise what he saw. The anger from Dean that he'd displayed was just a defence mechanism, Sam understood that now; when Dean showed anger, it often meant that it was an attempt to quell the fear that he was really feeling.
Sam ran a hand through his hair and blinked back tears as he remembered how things used to be. He stood up shakily and wondered over across the room to the cracked shards of mirror hanging reluctantly on the wall. Broken, Sam thought. Just like me. Things had grown worse and worse over the period of the next year or two following that. Dean's almost unnervingly calm reaction when he discovered Sam's addiction to demon blood...which ultimately set the stage for the big fight between them. Sam, turning his back on the only family he had left – and starting the Apocalypse as a result. As Sam looked at himself in the mirror he could barely recognise himself, but he was well aware of the fact that he now hated himself perhaps any more that anyone else ever had. His eyes searched the features of his face; the dark, permanent shadows under his eyes, the stubble that had been neglected enough to start forming a beard. In short, the life had left Sam Winchester.
It had taken a few days after his last conversation with Dean nearly five years ago for this all to sink in for Sam. He felt he had destroyed himself, a broken shell that wasn't half the man he used to be. He had been semi aware for a brief period that this was an irrational viewpoint, that it wasn't as bad as he thought...but the strength to hold onto that belief had disappeared from his life not long after Dean had. He realised that he needed Dean in his life, not only to help him get perspective, not only to save him from himself, but simply to feel alive.
And now Dean didn't want to know him.
If he did, he would have found the opportunity in the space of five years, right? Sam looked down from the mirror, unable to face his own reflection any longer, and staggered back to the tired, collapsed sofa by the table. The only thing in the room was Sam and the whiskey, and he had grown numb to the pain that that thought used to bring. He'd always had a weakness for addiction, and it had become even clearer since he and Dean had been apart. Drinking helped to make Sam oblivious to what was happening to him, as if a few swigs of whiskey would change what he'd become. But Sam liked it nonetheless. It was better than reality.
Reality was where he was the guy with the demon blood. Reality was wear he was Lucifer's "meatsuit". Reality had crushing weights attached to it.
Sam began to take gulps, welcoming the golden brown liquid into his system like an old friend. He'd had plenty of time to practice, and plenty of reasons to do it. That was enough. Sam's vision started to blur about an hour or two later...or maybe it had been longer. Sense of time was lost as he drank more and more into the night. Finally, unable to hear his own thoughts screaming abuse at him for any longer, he fell thankfully into a drunken sleep.
This is what Sam Winchester was now.
"Sure, it's good to feel things. And if it hurts, we're doing it to ourselves...or so the saying goes .But there should be a different music here. There should be just one safe place in the world. Tell me, how all this, and love too, will ruin us."