Spike turns human - Willow turns into a demon

What I can remember of this story. Spike starts to turn human, maybe because of a ring or necklace, that an elderly lady gave him. Willow steals the necklace/ring and does bad stuff. Spike ends up turning human and Willow ends up a demon, I think. Anybody remember who the author is/which story this is? Thanks.

Chiaroscuro by Miss Murchison

I think it is this, an old lady gives Spike a talisman that helps you become what you really are or some such, Willow steals it. I never finished it but it sounds like the one. It isn't letting me post links but it is on...

www . athenewolfe . com/justrewards/viewstory.php?sid=367

That is the story. I'm not sure if I ever finished it either, but I'm going to give it a go today. THANK YOU!