After defeating the Leviathan, Sam can't find Dean. But he tries everything. He hardly sleeps these days. He buries himself in research, but it does nothing. Sam is afraid if he stops, he won't be able to start again. And he can't do that. Not to Dean. Dean would never rest until Sam would be found. So that's exactly what Sam is going to do.

Set in season 7, Dean finds amnesia!Cas, but doesn't tell him who he is.

Late Destiel Christmas one-shot.

Dean and Castiel hunt a witch while undercover as a married couple.

Castiel thinks he isn't wanted anymore, but Dean convinces him he is.

Sam is caught in the middle of another one of Dean and Castiel's arguments.

Sam wakes up somewhere he doesn't recognize.

Dean hugs Castiel.

Cas didn't come back right. He won't tell Dean how he got out of Purgatory, and it scares him. But it doesn't scare Dean as much as how different Cas is.

After Chuck and Amara leave Earth, things go back to normal. Sam and Eileen are traveling to Ireland. Dean's even fallen in love with another Hunter. Everything is good. Everything is normal. But Castiel doesn't have a place in "normal." Without telling anyone, he decides it's time for him to return to Heaven, but things don't work out the way Castiel had hoped.