Is it Hell or High Water by electric_ink? Summary: Wherein Dean and Sam are killed by forces unknown (again), and Castiel is willing to do just about anything do bring them back. However, things aren’t quite as straightforward as they seem, and the civil war in Heaven reaches an unexpected climax when Raphael shows his hand. A story about faith, morality, and the ultimate cost of free will.

http://ink-electric.livejournal.com/3359.html