Setting
The first part of the book focuses mainly on the theme of identity and introducing the characters. The identity of the main character, Poirot, is not presented in the first chapters. Perhaps, the author used this method to emphasize his detective capabilities instead of merely stating his talent. Poirot needs to travel to London and takes an almost fully booked carriage. The readers are later introduced to a set of other passengers who are noted to be strikingly different in regard to their gender, assumed ethnicity, origin, and background. One of the passengers who approach Poirot are Ratchett and his secretary; even though Poirot took an interest in a couple, they disgust him due to their apparent arrogance and self-entitlement that Poirot finds repulsive.
Eventually, Ratchett asks the main character to protect him due to the death threats he receives, and Poirot denies the request. However, the concerns were correct, and the next day, after a troublesome night, Ratchett is found dead from twelve stab wounds. Although all characters are different, they develop a sense of unity in finding a murdered, contributing to the overall theme of identity. Despite their differences, they find common ground and share information, which hints at a shared secret between the passengers. The purpose of the introduction is to establish a setting.
Clues
The second part of the narrative focuses on the start of the investigation. The purpose of the section is to introduce the readers and Poirot to a set of clues that later will be pieced together to uncover a mystery. Firstly, Poirot interviews the secretary of the deceased, McQueen, and discovers that throughout their work together, the secretary suspected that “Ratchett” was an alias, and he was escaping from something. As one of the first clues, McQueen presents the detective with one of the death threats received by Ratchett, which turns out to be written by several people.
Upon closer inspection of the murder scene, the detective discovers that the deceased has been stabbed multiple times by both right and left-handed people, indicating that there has been more than one murderer. Furthermore, more clues are discovered: a handkerchief with an “H.” initial, different matches, and a piece of paper that says “remember Daisy Armstrong,” which helps Poirot to uncover the real identity of the deceased. In the following chapter, Poirot lunches with Dr. Constantine and Bouc, who also investigate the murder, and explains the real identity of the deceased – Cassetti. As it turns out, Cassetti kidnapped a daughter of a wealthy Armstrong family and requested ransom but killed Daisy regardless of receiving the money. After the accident, the mother, Linda Arden, suffered a miscarriage, and her husband and a nursemaid committed suicide, while Cassetti remained not convicted. The section presents readers with clues as parts of the puzzle and allows them to guess the murderer and their motive.
Evidence Gathering
Unlike a previous one, part three describes how Poirot actively gathers evidence instead of passively observing it. He interviews Pierre Michel, a conductor of the wagon, to discover that he saw the deceased at dinner and then visited his room per his request but was let go shortly afterward. The conductor has visited Mrs. Hubbard and Poirot after they rang a bell, made Ratchett’s bed, and saw a woman in a red kimono in the corridor. Pierre ensures the detective that the train was searched and the murderer already left the train. Upon the second interview with Ratchett’s secretary, Poirot discovers that he has an alibi, and McQueen’s father was an attorney working on Armstrong’s case. Lastly, he also reports seeing a woman in a kimono. Interrogation of Ratchett’s valet does not yield any significant results: he was laid off by his master the night of his murder and asked not to disturb him the following morning. The detective also discovers that the valet is a smoker.
Mrs. Hubbard, a passenger of the same carriage, interrupts Poirot’s interrogation and claims that she saw the murderer in her compartment who left a conductor’s button as a piece of evidence. Greta Ohlsson confirms her story and confesses that she accidentally entered Ratchett’s chamber at 10 pm and saw him reading. When Poirot questions the conductor about the lost button, he finds that the evidence is not connected to him. Princess Dragomiroff, Ratchett’s neighbor, states that although she went to sleep early, she expresses her concerns about the communication door between their compartments and suggests that it is the way murderer might have accessed Ratchett. In this section, the author attempted to confuse the reader by giving an abundance of opinions and points of view, which perpetuates the intrigue and complicates the plot.
Discovery
The last part of the story aims to piece all the evidence together to uncover an unexpected ending. Following the interviews of the aforementioned suspects, Poirot continues to examine the carriage’s passengers. After all of the meetings are completed, he sits with his companions and tries to piece all the gathered evidence. Poirot discovers a red kimono on his bed and concludes that the pipe cleaner and kimono clues have been forged evidence aimed at distracting him. As a result of his observation, he confronts one of the passengers, Countess Andrenyi, who turns out to be Helena Goldenberg, Mrs. Armstrong’s sister. Despite the lies about her identity, she claims to have no connection to the murder, and Poirot believes her. Later, an owner of the handkerchief, Princess Dragomiroff, confesses that it is hers but also denies any participation in the assassination. Upon the following inspection, Poirot discovers that every person has a connection to the Armstrong family. All passengers worked for or were a part of the Armstrong family and decided to enact justice on their own by avenging Daisy’s murder.
During all-passengers gathering, Poirot presents two options for the solution to the case. Firstly, the assassin might have entered their train on one of the stops, killed Ratchett at approximately one in the morning, and left the carriage unobserved. On the other hand, a more likely solution is that the Armstrong household with Linda Arden, Daisy’s mother, in the lead all killed Cassetti to avenge Daisy’s assassination. Although the passengers confess that they lied about their identities and killed Ratchett, Poirot and the other investigators decide to tell the police the first solution to protect Armstrong’s justice. The purpose of this ending, along with the whole work of literature, is to show that justice is not necessarily enacted by law but by hurt individuals who decide to perform their punishment. While it is illegal, ethical reasons allow them to seek revenge due to their loss.