All I can say is...
I revised my synopsis in the light of Vanda's comment and emailed it to the lovely, lovely Sally Quilford for a second opinion.
And she liked it. And she said it made sense. And she's going to help me make the synopsis even clearer.
Oh thank God (for Sally). I was thisclose to dropping the whole novel last night. But now...(and I would skip around the room if I wasn't such a lazy arse)... I feel re-motivated and enthused.
And thank God for Vanda. If I hadn't sent my synopsis to her I would have had no idea that there was such a glaring and confusing hole in my plot. Sending your work out for other people to look at is extremely scary...but it's worth it. Sometimes you're just too close to your novel to see it clearly.
Right, that's it for now. I've got some words to write.
Edited to add: A.Writer - thank you soooooo much for your email. You made my day!