As much as I think I can plot out a novel, characters still do things to surprise me.
A character called Old Col has been behaving badly all through this WIP, and I didn't know why. It was seriously annoying me - and Ondine, the main character.
Suddenly, yesterday morning, Old Col confessed the reason for her two-month-long bad mood.
And it's a doozy!
Plus, it all makes perfect sense, going right back to the first book.
This is how my novels and characters work. I plan out what I can, and then when they're ready, the characters tell me what's really going on.