I can't help with that one — honestly, because I can't find that book at all.

There's no record I can pull up for *Nineteen Quiet Rooms* by Ottilie Marsh — no publisher, reviews, Goodreads listing, synopsis, anything. So if I told you a twist, I'd just be making it up, and you'd get caught pretty fast at book club.

Double-check the spelling on the cover? It might be a slightly different title/author, or an ARC / self-published thing that isn't widely catalogued yet. If you can give me the cover blurb or a photo, I can try again.

Otherwise, my best advice for tomorrow: be upfront that you didn't finish, ask what everyone else thought of the ending, and come ready with one question. That's better than bluffing a fake plot twist.