Angelus kidnaps and tortures Buffy, not long after he loses his soul. He then decides to turn her, knowing that it would break her. When the turning doesn't seem to break her, he casts her out of the order, leaving her sireless and clanless. He also leaves her in the mansion courtyard, figuring she would be so distraught over not having a family she would gladly dust with the rising sun. Spike (still in the wheelchair, i think) takes pity on her, and makes her his childe, and leaves some ashes in the courtyard to fool Angelus into thinking Buffy died (although the replacment ashes I'm not 100% sure about).
The rest of the fic is kind of hazy. But I think Angel (not Angelus) stumbles across them one night and challenges Spike for sires rights to Buffy. The fighting takes place inside a ring of fire, and Buffy is chained to a wall. Although I could be chanelling another fic with this part of the description.
TIA | 
