I don't want to send you into book club with made-up information, so I'll be straight with you: I'm not familiar with *Nineteen Quiet Rooms* by Ottilie Marsh, and I don't have reliable details about its plot or ending. Rather than invent a twist that might be totally wrong (and embarrassing), I'd rather admit I don't know.

A few options that might actually save you for tomorrow:

1. **Skim strategically** — Read the last chapter or two, plus the first chapter, and any chapter titles that suggest a climax. Even 20–30 minutes can give you the ending.
2. **Search for a summary or reviews** — Goodreads, LitHub, or publisher pages often reveal key twists (with spoilers, which is what you want right now).
3. **Honest deflection** — At book club, say something like "I'm still forming my thoughts on the ending — what did everyone else make of it?" People love explaining twists.
4. **Ask a fellow member beforehand** — Someone in the group has clearly finished it; a quick "no-spoiler-free-zone, I need the twist" text might work.

If you can paste in the book's description, the final chapter, or even fragments you remember, I can help you piece together what happened and prep a few things to say.