Sam stumbles back, and his heart breaks in two against his will. But instead of being angry, shoving forward and doing what Dean wants, Sam just stares at Dean like it all has to be a huge misunderstanding; looks at Dean imploringly but can't bring up the right words for this -- because what are the right words? Everything he's ever feared is right here in front of him: Dean, turned, forced to become a monster, and Sam, a monster already, sucking down blood? Getting his brother changed? It's the bad end, one he was scared of, one he anonymously ran to the ship for, but nothing would make it any better.

Sam takes another step back and then his head throbs sharply. He thinks he's about to get hit with another dose of visions, but instead everything just blurs in and out of focus and he blinks hard -- just as his nose bleeds steady down both nostrils, plipping quietly on the floor under him. It takes him one second to realize how much he's fucked up, just being here.

He looks up at Dean with wide eyes.

This was a mistake.