A while back , maybe a year or so ago I found a Star Trek/ Spn fic where Dean was bound somehow to not die until he'd finished something (I don't remember this bit very well) but it took place in the Star trek time so there was no Sam. The title might have had *earth* in it somewhere. Dean and Cas hunt together trying to do whatever it was that Dean had to do. McCoy is a Nephilim and a church in San Francisco? is destroyed by an Angel/Demon battle and the news attracts Kirk's attention and he bullies McCoy into coming with him to see it. While there, they hide and overhear a conversation between Dean, Cas and another angel, who is female, higher ranked than Cas, and(I think) has a southern accent. Kirk thinks they're insane, but McCoy knows better. I don't remember much more than that other than I'm pretty sure it was part of a fic exchange or big bang type thing.

I had it bookmarked at one time but I had to get my computer serviced and the shop that did it deleted Firefox and all my bookmarks with it "because Internet Explorer is a better program". I lost a lot of things I've never been able to find again.


ETA : Found!