Dude Looks Like A Lady

Season 9 AU(ish). Castiel returns to the bunker, and finds out that Dean and Sam are still fighting. They go on a case, but find something unexpected that changes what they know about themselves - and how Dean and Castiel see one another. Unbeta'd. Warning: Slow build DESTIEL, Fem! versions will make an appearance, M for smut and swearing. Disclaimer: I do not own Supernatural.