 As with And Then There Were None, Lead Designer Lee Sheldon introduced a new character to the plot of Murder on the Orient Express, who was not present in Christie's novel, in order to fulfill the role of a player character and protagonist. The character, Antoinette Marceau, is described by Sheldon as an amalgam of two characters from the novel. These were Poirot's friend who ran the Orient Express, Marcel Bouc, and a young soldier who is present in both the novel and the film version of the story, who shepherds Poirot to Istanbul. Sheldon stated that he did not want to create entirely new protagonists for the Christie games, but rather preferred to draw from sources in Christie's novels to piece together the games' protagonists. Sheldon also addressed concerns from several early previews of the game, which asked why the player could not actually play as Poirot. He explained the choice of Marceau as the protagonist, saying "the reason for choosing Marceau over Poirot as the protagonist is that most of the fun of Poirot is seeing what he is up to, watching how he acts and solves things. I 've always thought the more interesting character was the' Watson ' character rather than the Sherlock Holmes character."
