Assassinio sull'Orient Express [Murder on the Orient Express]

There's a murderer on this train... or maybe more than one! Two passengers have been missing since yesterday, and the body of one of them was found last night. Hercule Poirot advised the engineer and the police officer on the train to gather everyone, including himself, in the dining car. However, before the dining car door is closed, you receive a message from Poirot saying: "Don't go with the others to the dining car. If I'm right, the murderer may be here with us, but the proof of his guilt is not. I've left you a letter with all the information I've gathered so far, and I'll keep everyone busy for an hour pretending to question them, so you can track down the culprit! Good luck!"