S11E01 - The Mystery of the Blue Train

The television film includes several changes from the original novel. In the film, Ruth's lover is traveling on the train with her, and they are both fleeing her husband. Ruth becomes friends with Katherine Grey. They switch train compartments, and when Ruth is bludgeoned to death, making her features unrecognizable, Poirot speculates that the intended victim may have been Katherine. Rufus, Ruth's father, has a wife in the film, who became insane after the birth of Ruth, and Rufus has ensured her (his wife's) safekeeping at a convent, where she has become a nun. New characters were added to the film; at one point, one of the other passengers visits Rufus' wife, who mistakes the passenger for her daughter Ruth. At the end of the film, the murderer dies, instead of just being arrested by the French police as in the novel.