Buffy and the Scooby Gang had been tasked with defending a key that can open the doorways to all dimensions all at once, effectively destroying humanity in an onslaught of demons, from the mad Goddess, Glory. However, the key was made flesh and the universe now believes- including Buffy herself- that they have known Dawn all their lives and that she is Buffy's younger sister.
During the final battle, Buffy sacrificed herself to save the Earth, but months later Willow, now a powerful witch struggling to control her powers, believing that Buffy's soul would be trapped in a Hell Dimension, casts a powerful spell to bring her back. Unknown to everyone, Buffy was actually in Heaven, and being torn back to this reality has left her less than she used to be. She keeps this a secret because she knows her friends wouldn't be able to cope.
The vampire Spike, evil but in love with Buffy, tries to walk the line between evil and being good and is the only one who knows the truth.
Willow has also cast a forget spell on her lover after a massive row about her use of dark magic.
Secrets are about to be revealed when a demon who can grant any wish is accidently given the talk of making life a bit of a song...