I don't recall the author or title, but I'd love to read the fic again, if anyone can help. What I do recall is that Xander was in LA with the Angel gang, and he was kind of damaged mentally, cos he went to some sort of BDSM club to be whipped and generally punished. I also remember a haunted apartment, though I'm not sure exactly how that fitted in.
There was something about the person who ran the BDSM club (?) being interested in having Xan for himself.
Sorry to be so vague, but hopefully this will jog someone's memory.