Sam's head feels like a boulder as he tries to lift it, his vision blurry as he sees Dean smirking back at him, bloodied and-- No.

No, it's not Dean. Just his body, his features pulled into a twisted grin, eyes dark pools of black because, once again, Sam has failed him.

"You won't," Sam says, his voice shaky and winded as he stumbles back to his feet, every muscle in his body aching, every nerve on fire. The blood in his veins is still pumping, still swirling. But he can tell he's weakening. And fast. "I won't let you."

Lifting his arm again feels like lifting the Impala one-handed, Sam grimacing through the pain as he calls up the power inside him again, searches for those dark, slimy tendrils coiled tight inside his brother's body, desperate to pull them apart one by one. Desperate to save his brother.