Dammit. I love this story and I hate it. I just want it out of my way so I can write something else.
If it won't go away, there's probably a very good reason. :-/
(don't you hate people who point out the obvious like that??) ;-)
I think some books can't be planned. Some are cathartic. Some are inspired. Some are like seeds planted by little demons.
You can try telling yourself YOU are the master of the situation. Never worked for me, but what the hey...
Go fo rit. Give your permission to write crap..just let it all flow out....and I bet you'll be surprised how it really Isn't crap when you're done.
Exorcise it or sell it.
You knew that.