Before I start writing (these days, anyway) I need to know the beginning (obviously) and some idea of the ending, but not necessarily everything that happens in between. Nothing is set in stone, though, and either may change before I’ve finished, depending on what happens along the way.
The two novels I’m prepared to own up to came about in quite different ways. The first (the one you’ve just read, Jane) started with the setting, inspired by a farmhouse I’d seen not far from where I live. It wasn’t derelict, but it was very isolated, and it started me wondering what it would be like to live in such a place, far from help, if things turned toxic. Then I thought of making it a ghost story.
The other came about in a much murkier and more indirect way. Short of inspiration for a follow-up, I dusted off an idea that had been knocking around for many many years. By the time I’d ‘finished’ it just about everything except the basic premise of the MC’s initial situation and a couple of characters’ names had changed. Including the genre.