I was thinking about this fic eariler, but well, I don't remember where I read it, so here.
I remember that Xander let his inner hyena play out in it, and it was set somewhere in S4, post-chip.
It went like this: Spike and Angel (who are having sex in secret), comment on Xander acting strange. Xander, meanwhile, decides to seduce them both. He first corners Spike (and proceeds to have hot sweaty fun), then corrals Angel in the mansion. Spike, who had been following Xander, curious about his strange behaviour, peeks over the window, and thinks that 'Harris looks like a fantastic shag'.
On the other hand, Anya was worried because the quantity of orgasms she was receiving from her boyfriend had diminished quite a lot (from 2 to 4 every night to virtually nothing), and wants to see where her orgarsm are going. She catches they three doing it.
Any ideas? Thank you all!!