It's temporary, or so they've been told. Dean'll get his voice back in a few days. Until then, Sam's making the most of it.
The silence in the library is his favorite part. No bitching, no running commentary, not so much as a sigh as his brother scours books of magic.
Dean knows he doesn't need to look for a cure, but he feels helpless if he's not doing something.
So Sam leaves him to it.
It's after midnight, and Dean shows no signs of stopping. Sam gets up, heads to the kitchen to make a pot of coffee.
Sets a steaming cup down in front of his brother.
Dean looks up, smiles gratefully, and brings his right hand to his chin.
Signs 'thank you'.
Sam's jaw drops.
He shouldn't be surprised, really. He knows, better than anyone else, how observant his brother really is. Eileen was here for long enough that Dean was bound to pick up at least a few signs.
"You're welcome," he says. And then, "Goodnight, Dean."
There's a twist of a smile at the corner of Dean's lips as he looks back at his book and signs 'goodbye'.