This idea has been hanging around for a while. so I've finally decided to grant it status on my "to be done" list. It's called Dulcinea (may change this name).
It's a retelling of the story of Dulcinea after Don Quixote has been taken away and "made sane" again. While she thought she would be relieved once the crazy man who has made a havoc of her life has been taken away, she misses seeing the world through his eyes. She convinces Sancho Panza (who also finds life duller without the Don) into coming with her and rescuing the Don from the people that are "healing" him.
They arrive too late. Don Quixote is no more, and it is only Alonso Quixano that they find. They spend the rest of the book trying to get Alonso to turn back into Don Quixote.
Since it's a retelling, it won't be set in the same time and place, which means the names will have to be changed. I also kind of like the idea of setting it in the future. That's the bones, anyway. I'm not sure where I'll be going with it.