A wounded Castiel calls Sam for help, with a request for Dean to stay behind. Naturally, Dean goes anyway and the brothers find their angel—now fully human—seriously injured with no grace and two wounds where his wings used to be.
Castiel isn’t talking, so Dean and Sam are left to figure out who took their angel’s wings and why. When they finally do figure it out, the truth gives Dean the courage to finally tell Cas how he feels.