I thought I had guessed it with about 80 pages to go. I gave my boyfriend a summary of what was going on and he jokingly said

12 passengers and 12 stabs? What if they each stabbed him once

We had a laugh about how ridiculous that would be. 🙃

The ending was cute but I have to echo some criticisms from other reviews. Guessing the truth somewhat randomly and hoping that the murderer confesses out of shock hardly seems like a plausible strategy. Someone else said it would’ve been better as a short story without all the drawn out interviews and I agree.