Some Kind of Disaster

Sam has been acting strange all day, constantly finding excuses to be away from Dean when they're supposed to be working a case. Every time Dean asks, Sam insists it's just a headache, and when the constant lying pushes Dean right up to his limit, he calls for backup.

Once Castiel and Sam are alone, Sam readily admits he's much sicker than he let on and explains there's no point in hiding it from Castiel because, well, Castiel doesn't care if Sam is sick and would never allow it to jeopardize a hunt the way Dean would. Castiel isn't sure how he feels about the accusation, but even more troubling than that is the way Sam's symptoms keep getting worse.