Murder on the Orient Express

Murder on the Orient Express is a classic locked room mystery, a type of crime common in mystery fiction. In these narratives, the crime occurs in a place and in a way that makes it impossible to determine how the criminal arrived to and left the scene. The literal example would be finding a dead body in a locked room: If the person is dead, the door is locked from the inside, and there’s nobody else in the room, how can a murderer have gotten in?

The locked room concept is seen in two ways in this book. First, there’s the question of how the murderer got in and out of Mr. Ratchett (Cassetti)’s room without being detected. Second, there’s the question of the train itself being a sort of “locked room,” due to the surrounding snow. The original crime is planned in a way that suggests an external party entered the train and carried out the murder. However, the snow ruins this plan: Because there are no footsteps in the snow going to or from the train, it’s clear that the murder was carried out internally, and not by an external party, and the snow creates an additional pressure to solve the case before help arrives.

This locked room element also impacts the way Poirot carries out his investigation. He can’t take steps to corroborate the stories of the passengers while the train is isolated. Rather, he must rely more heavily on the clues he can gather within “the locked room,” the train itself. Unfortunately, many of those clues mean testimonies from the passengers themselves—who may be lying. This brings the psychological element of detective work to the fore.