I've had an idea for a book kicking around for a while, and now--when I really don't have time to work on it--it's starting to gel. I've been trying to put it in the back of my mind to simmer some more, but I've got the main character's voice now and she's starting to get talkative. As of today, I know she's been living in L.A. for nearly ten years, her parents are new-age flakes who live in Montana, and she's recently divorced and wanting to start over in her old hometown. And I know she's going to run into her old best friend (a successful lawyer, divorced with two kids) and that she's going to get a crush on a coworker. I still don't have names, and I haven't worked out the murder (or even who's going to get murdered--yeah, it's a mystery), but that'll come later once the characters are worked out. And the characters won't leave me alone, dammit.
This is all rather distressing, because even though I've decided to jettison the rewrite-from-the-ground-up of the fantasy novel I was planning to sub to Wizards of the Coast (I sent a different manuscript instead), I've got another project all set up for Nano. I've done Nano two years now and had a blast both times; I want to start working on plot for this year's project in October so I'll have my outline ready by November 1. But I can't plot that project if I'm plotting a different one; I've tried working on two novels at once and it doesn't work.
I think my only recourse will be to start plotting my Nano book now. With luck I'll get so excited about it (and it's going to be a lot of fun) that it'll push my new mystery to the back burner for a while.