Murder on the Orient Express

In Murder on the Orient Express, Poirot’s primary work is psychological. Poirot highlights the psychological aspect of his role on more than one occasion. He consistently notes how the suspects appear to him, and then ruminates on the psychology behind their motives. At first, most of the passengers seem to have air-tight alibis provided by other passengers who had no surface-level reason to vouch for their whereabouts. When reflecting on his interrogation of MacQueen, Poirot is convinced that the secretary could not have been involved with the murder. However, Poirot remains suspicious of Mary Debenham and Colonel Arbuthnot because they’re unwilling to reveal the topic of a hushed conversation Poirot overheard. This suspicion, though confounding to Bouc and Dr. Constantine, is rooted in the psychology of the investigation for Poirot: He understands that Debenham and Arbuthnot are willing to hide a conversation, so what else are they willing to conceal?

The crime’s methods themselves also reveal the psychology of the victim’s murderer. Poirot disagrees with Bouc’s assertion that the crime was one of passion. He recognizes the crime to be methodical and planned, with planted clues such as the handkerchief and pipe cleaner. Through observation of the scene, Poirot is able to detect which clues were not planted, such as the match that was used to burn a letter to Mr. Ratchett (Cassetti) revealing the ties to the Daisy Armstrong kidnapping case.

Through logical deduction and crucial attention to detail, Poirot is able to unravel the ties that bind the 12 passengers together. Bouc’s comment about the “romantic” melting pot of the train’s many nationalities represented in its passengers begins a line of thought early in the novel. Poirot is able to separate his impressions of the passengers, such as his thoughts that MacQueen and the Colonel could not be involved with the stabbing and his attention to the subtle psychological slips by key passengers. For example, Mary Debenham, a reported Englishwoman who never visited America uses the American term of “long-distance” for calls, while Hildegarde Schmidt admits that all her ladies admitted she was a good cook—an unknown admission that she was not a true lady’s maid, since lady’s maids don’t cook.

Dr. Constantine’s examination of the victim’s body confirms what Poirot learns from monitoring the passengers’ actions and slips of phrase: The crime was committed by many people, as seen in the varied stab wounds that seem to disconnect with one another. As 12 people were stabbing Mr. Ratchett (Cassetti), no one wound is like the other, reflecting the individuals who made them and the psychological factors behind their actions.