I have to be honest with you here: I'm not familiar with a book called *Nineteen Quiet Rooms* by Ottilie Marsh. It's not something I have reliable knowledge of, and I don't want to guess at a twist and send you into book club with made-up plot details — that could go badly for you!

A few possibilities:

- **It might be very recent or from a small press** — my knowledge has a cutoff, so newer releases sometimes aren't on my radar.
- **The title or author might be slightly off** — worth double-checking, since book club announcements sometimes get garbled.

Since your meeting is tomorrow, here are your fastest options:

1. **Goodreads reviews** — reviewers often discuss endings, and you can sort by spoilers. Sometimes people explicitly write "the twist is..."
2. **Search "Nineteen Quiet Rooms ending explained"** — thriller-ish books often get ending-explainer articles or Reddit threads.
3. **Ask a club member** — even a "hey, I want to come in fresh, can you give me the gist of the last few chapters?" to someone who finished it.
4. **Skim the last 30–40 pages yourself** — often enough to catch a twist even if you missed the buildup.

If you can tell me roughly where you stopped reading or what the book's premise is, I'm happy to help you think through what you've got so far — or if the title turns out to be something else, let me know and I'll see if I actually know it!