“Only by interrogating the other passengers could I hope to see the light, but when I began to question them, the light, as Macbeth would have said, thickened.”
Aboard a train for the night, legendary detective Hercule Poirot (Albert Finney) is interrupted on his vacation to solve a murder. A timely snowdrift allows the detective to question each of the passengers one by one.
As Hercule Poirot deduces, each of the passengers that he questions has some link to the murdered man, Mr. Ratchett (Richard Widmark). All of their lives correspond to the life of little Daisy Armstrong, whose death set in motion several other deaths. Though Mrs. Hubbard (Lauren Bacall) assists the detective with a missing tunic button and the insistence that a man crept into her compartment the night of the murder, Hercule Poirot discovers that each of the passengers had a motive.
Unlike Clue, Murder on the Orient Express offers a meagre relationship with each of the suspects. None of them seem remarkably innocent, but unlike their dead co-traveler, none of them seem remarkably guilty either. What humbles Hercule Poirot is the notion that this particular dead man deserved exactly what he got.
Collective guilt or guilt by association is the idea that a burden of responsibility is carried by a group of people for the actions of one person or several other people. Cultural guilt plays into this; white people in the wake of Black Lives Matter carry collective guilt about the way their race has historically mistreated black people.
In the case of these fictional train passengers, their responsibility for the deaths of Daisy and four others is believed to be assuaged by the death of the kidnapper, Mr. Ratchett. In a strange turn of morality, Hercue Poirot allows the passengers their peace of mind by suggesting that his offer to the police will be that a strange man snuck onto the train and committed the murder. Collective guilt, the film suggests, can be redeemed by the same group that carries it, if only their idea of justice is agreed upon by famed investigators.