Hercule Poirot
This Belgian detective, who sports a signature mustache and a genial personality, is a recurring character in Agatha Christie's novels. He has unusually sharp observational skills, a keen ability to read others' emotions, and immense logical abilities. Poirot presents himself as meticulous and eccentric, and despite his reliance on quiet and deep thought, he is an enthusiastic performer. In fact, after he has determined the likeliest truth through careful thought, he tends to fact-check himself by combatively confronting his suspects in order to watch their reaction. Though he is the book's protagonist, his inner life remains obscured from the readers, and indeed he is a somewhat flat character. His role is primarily to act as a guide for the reader, bringing evidence to the forefront and presenting it in a comprehensible order.
Mr. Ratchett
Ratchett, the story's murder victim, is actually an American gangster by the name of Cassetti. At the start of the novel, Ratchett asks Poirot for protection against his enemies.
M. Bouc
M. Bouc is an old friend of Poirot's and a fellow Belgian. He works for the Compagnie Wagon Lits, which owns the Orient Express. He is Poirot's constant companion, both serving to help him take charge of the train when necessary and acting as a stand-in for the reader. It is Bouc who asks Poirot to take the case of the murdered Mr. Ratchett. Bouc is routinely amazed by his friend's ability to solve mysteries.
Dr. Constantine
Constantine is a Greek doctor who is called in to examine Ratchett's body. Like Bouc, he keeps Poirot company throughout the novel and serves as a point of identification for the reader. It is Constantine who determines that Ratchett's unusual wounds were created by at least two killers. He also decisively gives the time of death for Ratchett.
Mrs. Hubbard
Mrs. Hubbard is an obnoxious, neurotic American woman who talks incessantly about her daughter, whom she has supposedly just visited in Turkey. Her testimony is pivotal during Poirot's investigation: she claims to have seen a man, presumably Ratchett's killer, hiding in her compartment on the night of the murder. She also claims to have found a bloody dagger hidden in her luggage. However, both of these revelations are revealed to have been fabricated or staged, as is Mrs. Hubbard's entire identity. As it turns out, she is actually Linda Arden, the famous tragic actress who was Daisy Armstrong's maternal grandmother. This makes her obsession with her (fictional) daughter all the more poignant, since she is in fact grieving for her real-life daughter.
Princess Dragomiroff
Dragomiroff is an elderly Russian aristocrat who is rumored to have fled her native country after the communist revolution. She is imposing, mysterious, and remarkably ugly, but with a manner that commands respect from everyone including Poirot. It later comes to light that she was the godmother to Daisy Armstrong's mother—one of Ratchett's victims—and was motivated to kill him for that reason. The mysterious handkerchief found in Ratchett's compartment turns out to be hers, though it is later revealed that this clue, like most in the case, was planted to confuse detectives.
Colonel Arbuthnot
Arbuthnot is a stereotypically English officer serving in India, which was at the time colonized by the British. He is quiet, stoic, and a bit snobby. His early conversations with Mary Debenham ignite Poirot's suspicion and inadvertently reveal that the train's passengers are not the strangers they pretend to be. Christie hints that, over the course of the novel, he develops romantic feelings for Debenham.
Mary Debenham
Debenham, like Arbuthnot, is stereotypically British. She strains to act composed and emotionally restrained, but her composure begins to crack early in the novel: Poirot witnesses her obvious distress, not only in her conversations with Arbuthnot, but in her reaction to the train's inevitable delay. She later runs from the compartment in tears during one of Poirot's interrogations. Poirot eventually realizes that she was employed as a governess in the Armstrong household.
Countess Andrenyi
The Countess is a very quiet, beautiful, and young woman with a vaguely foreign air. Her husband is a Hungarian diplomat, but she claims, unlike him, never to have visited the U.S. Her alibi crumbles when Poirot notices strange marks on her luggage tags and passport: she has, he realizes, tried to make it seem as if her name is Elena rather than Helena. As a matter of fact, the Countess is American, and is the younger sister of Daisy Armstrong's now-dead mother. Once this is revealed, her manner changes, and her mystique drops away to reveal an emotionally open, sensitive, and vulnerable personality. Despite her close connection to the Armstrong case, she is the only passenger who did not directly attack Ratchett. Rather, Poirot suspects, her protective husband has stabbed him in her place.
Count Andrenyi
The Count, who is older than his wife, is a Hungarian diplomat. He is not directly connected to Daisy Armstrong, but he is a doting and protective husband to the Countess, and therefore stabs Ratchett in her stead.
Cyrus Hardman
Hardman originally behaves like a stereotypical American, with a brash, crude, and overly familiar personality. While this personality never entirely disappears, he later reveals that he is actually an undercover detective with a New York City firm. He tells Poirot that Ratchett had hired him in an attempt to stay safe from various enemies. However, it later turns out that this persona, too, was a lie: though he is indeed a detective, Hardman was never hired by Ratchett. Rather, he was in love with the French nursemaid employed by the Armstrong family, who later committed suicide.
Greta Ohlsson
Ohlsson, an older Swedish woman, is returning from missionary work. She speaks very little English and appears intensely emotional throughout the proceedings, crying frequently. The real source of this intense emotion becomes evident later, when Poirot discovers that she was a nurse in the Armstrong household.
Hector MacQueen
MacQueen is Ratchett's friendly young American secretary. He frequently complains to Poirot about how his employer spoke no languages other than English, which turns out to be one of many attempts at misleading and misdirecting the detective. Indeed, it turns out, MacQueen specifically sought employment under Ratchett in order to help plot his murder. This is because MacQueen's father was a district attorney handling the Armstrong case, giving Hector firsthand knowledge of the family's heartbreak and Ratchett/Cassetti's evil.
Antonio Foscarelli
A talkative Italian man, whom Bouc immediately suspects, partly because of his nationality. Foscarelli, it later turns out, was a driver for the Armstrongs with an especially strong attachment to young Daisy.
Hildegarde Schmidt
A maid employed by Princess Dragomiroff, Schmidt is a kind but unassuming German woman. She seems primarily driven by loyalty to her employer, seemingly lying numerous times to protect the princess. However, Poirot later discovers that she, too, is in on the murder, having been a cook in the Armstrong house.
Pierre Michel
Pierre Michel is the conductor of the train on which the novel takes place. Bouc vouches for his trustworthiness, and for most of the novel he is assumed to have been uninvolved in the murder. He appears to be dutiful, organized, and helpful. However, it later turns out that he was the father of the French nursemaid who committed suicide during the investigation of the Armstrong case. Indeed, Poirot learns, Ratchett's killers chose the train as the site of his death precisely because one of their group, Pierre Michel, would be working on it.
Edward Henry Masterman
Ratchett's valet, Masterman is a quiet Englishman much like Arbuthnot—but with a humble, dutiful personality. Masterman prefers reading and being alone to socializing. However, he is later discovered to have ties to the Armstrongs: Masterman was Colonel Armstrong's servant, both when the two served in the military and back at the Armstrong home. Like MacQueen, he sought employment with Ratchett specifically in order to help arrange his murder.
