Ok, I'm posting another fic search... I'm sorry! This has been bugging me for awhile though, so I figured it was worth a try. In the fic, Willow goes evil because Tara dies, and kills Anya to take Dawn and give her to the Watchers so that she can harness the power of the key to help resurrect Tara. Xander kills her with a knife, but is vamped when he bleeds out, because Dracula had shared blood with him earlier. He then goes to LA, where Angel has vamped Lindsey. Thanks!