What happens when good and evil don't so much collide as merely annoy each other? Which, when young men are involved, quite often means that they really want to get to know each other.
Ash, a low level demon, and Cas, a low level angel, become aware of each other -- in more ways than one -- and set out to prove that good and evil can exist in close contact, even complementing each other. They blur the lines and cross them frequently with surprising and almost devastating results.