I'm trying to remember a Season 2 story. Spike kidnapped Buffy. Over the course of her capture, they develop feelings. One night, while they're sleeping, Angel steals in and stakes Buffy because he assumes she a vampire. Spike freaks out and leaves. Buffy walks herself to the hospital but picks up a trail of vampires....minions from where she was held and more that follow her to the hospital. None of the vamps attack her though because she belings to Spike.

I think you are after the WIP What Place is This by Megan (Peta). It is on this site.