The book opens with the third-person narrator introducing the hero of the story: famed detective Hercule Poirot. Poirot is in Syria, waiting for the Taurus Express train; he was in Aleppo to solve a case. Poirot boards the train and finds two other people sharing his compartment: a young British governess, Mary Debenham, in her late twenties, and an older English Colonel in his forties or fifties, Colonel Arbuthnot. Mary and Colonel Arbuthnot have breakfast together but don’t invite Poirot to join them. Poirot notices the way that Colonel Arbuthnot looks over him and reads the man’s view upon Poirot, a Belgian, to mean, “Only some damned foreigner” (9).

Later, Poirot overhears Mary and the Colonel having a curious conversation: When the Colonel tries to speak to Mary, she tells him, “Not now. Not now. When it’s all over. When it’s behind us—then—” (11). Poirot doesn’t realize it yet, but Mary is referring to the impending murder of another passenger on the Orient Express—the train that Poirot, Mary, and Colonel Arbuthnot will all board when they reach Istanbul.