From Fool For Love thru the end of Season 5. Buffy turns to Spike for love assistance and comfort as she fights a hellgod and the differences between vampires and Slayers. Spoilers for Season 5

That's how betrayal works. It sends out ripples of hurt. Ones right next to you...ones you can't even see.

A year after the events of Season Eight, Buffy is still reeling. But while she and Spike try to sort out the hurt and confusion that Buffy's been dealing with all year, the aftershocks of her betrayal have brought a new enemy forth...one that might just be the one to break her completely.