I am looking for a fic, where (I think) Travers kidnaps Buffy, Angel and Spike. He pumps some sort of gas that turns the vampire into their basic instinct. Instead of the intended fight over who gets Buffy, both vampires  "share" her. I can't remember why Travers kidnapped them but something about creating a powerful baby. I haven't read this one in years so it shouldn't be new. I think I read it here but I'm not sure.

Dreams and Nightmares by Abbyland