Original Sins: Lost Slayer Serial Novel part 4

HOMECOMING
Joyce Summers is dead. Spike has been slain and Faith, rogue Slayer, is gone as well. Southern California has fallen under vampire rule.
And Rupert Giles is Vampire King.
Buffy can hold no one but herself responsible for this grim possible future; her own insecurities and petty jealousies led to this moment. She must now gather her inner strength and combat the demon that inhabits the corpse of her most trusted mentor. With the help of Willow and the Slayerettes, Buffy must invoke the elements, stave off a vampire stronghold, and return to her real-time body -- but not before identifying and preventing the misstep that brought about the oppression of those she holds closest....
The Conclusion