Buffy's resurrection caused an instability which allows The First Evil, a spiritual entity that Buffy encountered before, to begin tipping the balance between good and evil. It has inactive Potential Slayers hunted and killed by Caleb, a sinister and misogynistic preacher turned serial killer who heads a cult called Bringers, who worship The First as a god. Inside the Hellmouth it raises an army of Turok-Han, an ancient and powerful sub species of vampire.

Willow resurrects Buffy with a powerful spell. Although her friends believe that they have taken her out of Hell, Buffy had actually been in Heaven since her death (a fact that is later revealed to her friends). She is therefore traumatized by her resurrection and this causes her to fall into a deep depression. Meanwhile Giles returns to England after realizing that Buffy has become too reliant on him, while Buffy takes up a fast-food job for money and develops a secret, mutually abusive relationship with Spike.

Dawn appears in Sunnydale as a younger sister of Buffy. No one finds this strange, but it is soon revealed that the teenager is a mystical energy called The Key that was transformed by a group of monks, using Buffy's essence, into human form. False memories were implanted in all those concerned to protect the fourteen-year-old from Glory, an exiled God from a demon dimension who wants to leave the human body in which she is trapped (Ben the hospital intern) for her home universe.