Poirot, world class detective, and the protagonist in many of Agatha Christie's mystery novels, is again at work in the novel, Murder on the Orient Express. Poirot arrives at the solution to the murder when he realizes that the entire train has taken justice into their own hands and because cassetti continually escaped punishment for his crimes, they executed him. Everyone on the train has a connection to the Armstrong family. However, they talk Poirot into telling the police a different version of the truth so that they can live their lives peacefully, having administered a long overdue justice.
