Fallen Angels by BuffyMeetsSpike
Goes off-canon during Bargaining. When Willow's spell pulls Buffy out of heaven, it leaves her insane, terrified, and unable to communicate. The Scoobies are convinced she came back wrong. Spike is convinced that he can reach her. And Buffy's misconceptions about this hell she has awakened to lead to a host of problems and heartache. Who will be the one who can guide this fallen angel back to life?
bloodshedverse.com/stories.php?go=chapters&no=13324
The Ghost in You by BuffyMeetsSpike
Goes AU during Bargaining. Willow's spell goes awry, leaving Buffy incorporeal, and visible only to Spike. With the Scoobies convinced that Spike has lost it, how can he help Buffy get back where she belongs?
http://bloodshedverse.com/stories.php?go=chapters&no=12645