Yesterday I finished another chapter, which left me with two to go.
Today, I sat down to work-- late, thanks to a migraine-- and realized that due to changes I've made throughout the book, very little of of what I had in this penultimate chapter is going to work.
I figured out what needs to happen, made an outline, and got about halfway through the writing, but now I've left myself with a chapter and a half to edit tomorrow. I may need to extend my deadline to Saturday. If so, it won't be the end of the world-- I'll just have nine days to fiddle rather than ten.