Hercule Poirot is one of the detectives that Agatha Christie devoted an entire series to. In this story, Poirot is simply traveling by train back to London from Stamboul (Istanbul). Suddenly, a murder is committed on the train and Poirot is forced into solving this case. Poirot is famous for his curly mustache, short stature, and clever, cunning intelligence.
Ratchett is the unfortunate murder victim with a hidden past that comes back to haunt him.
M. Bouc is the director of the Compagnie Wagon Lits, the owners of the train. M. Bouc is an old friend of Poirot, and eventually asks him to take on the case.
Dr. Constantine is the coroner aboard the Orient Express. Constantine does the official examination of the body and is often present, along with M. Bouc, when Poirot is gathering evidence.
Mary Debenham is an instrumental character throughout the novel. Debenham is one of the characters that has the most to hide from Poirot, though she cannot hide her past forever.
Mrs. Hubbard is the only American woman aboard the train, and is constantly talking to someone, about anything. Mrs. Hubbard continuously interrupts the investigation with overdramatic outbursts.
Colonel Arbuthnot is a strong, stoic Englishman who strikes Poirot as a potential suspect. Arbuthnot is previously acquainted with Mary Debenham, and Poirot is suspicious of their relationship.
Countess Andrenyi is young and beautiful, and perhaps the least-suspected person on the train...at first. As the story unfolds, so does the Countess' true history.
Cyrus Hardman is the flamboyant American man aboard the train. The reader soon finds out during the investigation that Hardman is actually a detective as well, though just who he is helping throughout the case isn't always obvious.
Antonio Foscanelli is the primary suspect of M. Bouc, simply because he is a large, intimidating Italian. M. Bouc distrusts Italians. Greta Ohlsson is a timid Swedish woman who cannot seem to stop crying for a significant period of time.
Hildegarde Schmidt is the slow maid of Princess Dragomiroff.
Pierre Michel is the conductor of the Orient Express. His role in the story is very insignificant in the beginning, though it grows exponentially as the story continues.
Now, with all of these characters listed, it's imperitave that as a reader you keep in mind that the story is a murder mystery, full of lies and cover-ups. Not everything, including these characters' descriptions, remain the same or are correct...