Buffy is pregnant with Spike's child, that or she just had the baby, I can't really remember, but I believe she just had the baby. And she has to go on the run cause the Inititive wants her and the baby for testing. She ends up hiding and Riley finds them in a hotel somewhere. He ends up kidnapping Buffy and the baby, and the baby bites him and marks him with a vengence bite, so that all Aurelian vampires know that he is marked for vengence and are compelled to give it. Spike ends up tracking them down in vegas and gets them away from Riley. Riley then tracks them to a basement in some hotel/club, and Buffy is compelled to exact vengence on Riley because of the bite. She starts to do that, but is stopped by her son who came from the future stating that if Buffy enacts the vengence then she forever feels the guilt of taking a human life and it ultimately destroys her in the future. Spike tells Buffy to leave the basement and he and the future version of his son do just that. I believe Drusilla is in the fic towards the beginning, and I think she actually helps Spike in tracking down Buffy, or helps Buffy in Hiding from the initiative.
TIA | 
