Exorcism

Dean Winchester comes back to Sam two months after becoming a demon.
When Sam finds out, he goes on a hunt with Dean to find out what's going on, but when Dean gets horrible flashes of his humanity, does Sam really want to find out? And why do these flashes always happen when Castiel is around?
Why is Dean lying and what's going on with Crowley?
So many questions, so little time.
So many answers that need to be found out that...
no one cares that Dean is broken.