Title: Topple

Disclaimer: Just playin' in the Winchester's world.

Summary: Season six story- Dean's thoughts leading up to end of 'You Can't Handle The Truth'. Spoilers.


He'd known almost immediately that it wasn't Sam, had known since he'd first clasped his arms around his little brother and felt nothing in return.

Still, he'd held on all the same because, hey, they were Winchesters, and hugging was what they did when one of them came back from the dead.

It unnerved him slightly, the lack of response from his brother, but Sam was back and that was enough. And so Dean ignored the little voice in the corner of his mind that said something was amiss, gripped Sam a little tighter and tried to imagine for a moment that all was right with the world.

He should have known.

There were signs of course. Spending nearly every minute with a guy for more than twenty-five years, you tended to notice the little things. The way Sam carried himself a little taller since he'd come back, the way his usually expressive eyes seemed empty and vacant, the way he'd suddenly become the perfect hunter, each was Sam, yet somehow not Sam.

Dean knew better than anyone what Hell could do to a person, and he'd only been down in the trenches... didn't want to imagine what it'd been like stuck in the honeymoon suite with Lucifer and Michael. It didn't matter how strong or brave or stoic you were, that changed a guy.

But Sam was…different. Not in a been-to-Hell-and-back (literally) way, but fundamentally different, and Dean couldn't shake that little voice that told him something was wrong.

Still, Dean had spent a year without his brother, a year filled with nothing but grief and guilt and pain, and now Sam (or something that resembled him) was alive and well and Dean decided he'd be okay with that.

So Dean told the little voice to shove it.

After the whole vampire thing, the voice was back, but this time it was screaming at Dean from every pore, NOT-SAM! NOT-SAM! And for the first time Dean looked, really looked, at his brother and felt himself grow cold.

It was Veritas who confirmed it. The bitch stared right at Sam and said it straight out.

"Not human," she said, and even though Dean knew it in his heart, hearing the words didn't make it any easier. He was suddenly reminded of the chocolate rabbit he'd swiped when he was 11, so beautiful and perfect on the outside, but on the inside, containing nothing but a hollow shell.

Just like his brother.

Dean could have laughed at the absurdity of it all.

Except it wasn't funny. Not in the least. And this…thing…wasn't the baby brother he'd fed and clothed and protected and died to save. This was something else, and Dean didn't quite know how to process that.

So he did what he knew how to do best.

He hit him.

And hit and hit and hit, as if maybe with each connection of his fist a small piece of his brother might get knocked back into the thing on the ground. Dean didn't feel his knuckles begin to shred, didn't hear the snap of bone as his not-brother's nose broke beneath his hand. He didn't feel much of anything, just focused on one punch after the other, focused on making the abomination underneath him go back to wherever it was dreamed up.

Dean wasn't sure of much anymore, wasn't sure of what was good or evil, or right or wrong or even where he fit into it all. But one thing he was sure of.

This?

This wasn't Sam.