I finished it a few weeks ago, and the central mystery hinges on who killed Macaire Ebezner and what that has to do with a secret society called the Spider. The story within the hotel is just the shell; the real secret is how the author himself, a character named Joël, gets entangled in the decades-old case.
It’s structured like a Russian doll. The murder at the Hotel Verbier is one layer, but the bigger revelation is about the interconnected fates of the Ebezner and Tarnogol families, all tied to a massive banking swindle. The 'key secret' isn't just the murderer's identity, but the fact that the entire investigation was orchestrated from the start to expose a different, more personal crime buried under corporate greed.
Honestly, the financial conspiracy stuff lost me a bit, but the final twist regarding the true relationship between two central characters and the real reason for the cover-up is what stuck with me. It’s less a whodunit and more a 'why-they-decided-to-let-it-look-like-a-whodunit.'