Work Text:
Nothing's changed.
Sam's an idiot to think that Dean's agreement to keep things strictly business would ever mean anything in the heat of the moment. As soon as Magnus gets near Sam, Dean goes crazy; when he cuts Sam, Dean's practically out of his mind.
As much as this is exactly the thing that Sam was talking about, it's almost addictive to see Dean's reaction, to know that no matter what things are like between them in the off-hours, Dean can't help wanting to protect Sam.
The second cut hurts, but it's there and forgotten, the first one throbbing on his cheek still while Magnus makes his threats. Dean's gone, though, and hope beats wild in Sam's chest. Dean's going to save him like Dean always does.
And then Dean can't let go. He's in there, fighting for control, Sam can see it, but there's something else pulling levers in Dean's body. "Dean?" The mark of Cain is red, burning bright against Dean's skin. "Drop the blade, Dean."
"Dean!"
Dean looks at him, like Sam knew he would, like Dean always does. When he says it a second time, Dean's there, nominally in control, and he's looking at Sam, listening to Sam. He drops the blade because Sam says so.
Nothing's changed.