Rated: M
Takes place in 'Slash Fiction', when the Leviathan has Sam trapped in the interrogation room.
It was Dean.
It walked like Dean.
It talked like Dean.
It was Dean.
But…
It wasn't. It was a Leviathan, a fucking Leviathan, and it was wearing his brother's face to kill him, and maybe that hurt more than if it had his face on.
The Leviathan was talking- something about Amy, Amy being dead, Amy being killed, Dean killing Amy- but, Sam just…he couldn't stand looking at Dean- his big brother, his hero- when it was a monster behind that familiar face.
Finally, the Leviathan seemed to clue into the fact that Sam wasn't paying strict attention to what it was saying. He grabbed Sam by the hair- and wouldn't Dad have something to say about that, letting his hair get long enough that something could get a good grip on it.
"Oh, no no no, Sammy, we listen when big brother is talking." the Leviathan hissed.
It was talking in Dean's voice, and it physically hurt Sam to listen to him, describe in bloody detail what the Leviathans were going to do.
"-but first, I'm going to fuck you, Sammy." The whisper, in his ear, in Dean's voice, made him flinch. "Oh, that got your attention, didn't it?"
Sam tried to shake his head, but the Leviathan had kept that tight grip on his hair.
"Don't try to deny it. You want Dean-o to fuck you. We're in your noggin, Sammy, we know everything. I'm going to slam you against this table, and fuck you, and you'll come, screaming Dean's name, and then, I'm going to kill you."
"…no…" Sam whispered, and the Leviathan grinned in delight.
"Yeeeeeeessssss. And I'm not just going to kill you, Sammy. I'm going to eat you. But let's not linger on that. Let's go back to the whole fucking you part. Let's say Dean-o somehow manages to get in here, just in time to play hero. Well…try to play hero. What do you suppose he's going to see?"
"Stop!" Sam tried to snap, but by now, the Leviathan was pressing him against the interrogation table, and all that came out was a weak wheeze.
The Leviathan ignored him, continued speaking.
"He's going to see him. Fucking his little brother into a table. And little brother is going to be moaning his name, begging him for more. And I'm not going to stop, just because big brother is on the scene, Sammy. Dean gets to watch, as I fuck you, as I kill you, as I eat you. And there's not a damn thing you can do to stop me, Sammy."
Later on, when the Leviathans were dead, and they were safe- well, as safe as a Winchester could get, nowadays, anyway- Sam chose to leave, rather than actually talk it over with Dean. Because even if the Leviathan was dead, Sam could still hear it whispering in his ear, describing exactly what he wanted from his brother.