There is a strict class structure in most Christie's novels and especially in Murder on The Orient Express. Class not only represents one's financial well being, but emotional. The servants are much weaker characters than then the non working-class passengers. Hildegarde Schmidt, Greta Ohlsson, Antonio Foscanelli and, eventually Mary Debenham all break into tears by the novel's end. None of the other characters get so upset about the situation, perhaps because they do not have to. If they loose their jobs, it is not such a big deal, as they are independently wealthy and most are not required to work. Mary Debenham even tells Poirot she does not tell people she was associated with the Armstrongs because she is worried about securing other jobs. Although the cabin is made up of "many different classes and nationalities," it is strictly divided into working class and aristocratic passengers.
Americans, at least the two admitted, are comedic characters in the text. Both Hardman and Mrs. Hubbard use improper slang, are fairly obnoxious and think their country is the best, both caricatures of American males and females. Mrs. Hubbard prone to calling people "folks," tells people that Europe needs Western ideals and Hardman, who constantly speaks in awkward slang tells M. Bouc he would "learn a few go-ahead methods over there...Europe needs waking up. She's half asleep." Poirot agrees that America is a place of progress, but it is clear this progress isn't always positive.
One of the greatest motif is Murder on the Orient Express is that of identity. In the first two sections of the book, the passenger's identities are assumed to be correct, but in the third section the real identities of the passengers are revealed. The motif adds to the surprise of the book. As Poirot admits, there are no standard ways of investigating this case, so he and the reader are forced to first accept the evidence as the passengers as truth. There is no way to see if they are lying or not. Most of the passengers tell the truth about their names, but not their professions or association with the Armstrong family. Countess Andrenyi attempts to smudge and change her name, Heleana to Eleana, and Linda Arden makes up an entirely fictitious character to play while on board the train.