In order to get a realistic effect, Sir Alfred Hitchcock insisted that there should be no background music except at the beginning and the end. Between those two points, the only music heard is the music sung by the musician outside the hotel, the music tune of Miss Froy, the "Colonel Bogey March" music hummed by Gilbert (Michael Redgrave), the dance music conducted by Gilbert in his hotel room, and the dance music when Iris (Margaret Lockwood) meets Gilbert in the train.
Charters and Caldicott (played by Basil Radford and Naunton Wayne) proved to be such popular characters that they were teamed up in ten more movies. They reappeared in Gestapo (1940) (also starring Margaret Lockwood) and Milhões Como Nós (1943), two movies also written by Sidney Gilliat and Frank Launder. They also starred in the BBC Radio serials "Crook's Tour (1940)" (which was also made into a movie), and "Secret Mission 609." They were played in the 1979 remake by Arthur Lowe and Ian Carmichael. In 1985 they reappeared in the BBC Television mystery mini-series, Charters & Caldicott (1985), played by Robin Bailey and Michael Aldridge.
In an interview with Peter Bogdanovich, Sir Alfred Hitchcock revealed that this movie was inspired by a legend of an Englishwoman who went with her daughter to the Palace Hotel in Paris in the 1880s, at the time of the Great Exposition: "The woman was taken sick and they sent the girl across Paris to get some medicine in a horse-vehicle, so it took about four hours. When she came back she asked, 'How's my mother?' 'What mother?' 'My mother. She's here, she's in her room. Room 22.' They go up there. Different room, different wallpaper, everything. And the payoff of the whole story is, so the legend goes, that the woman had bubonic plague and they dared not let anybody know she died, otherwise all of Paris would have emptied." The urban legend, known as the Vanishing Hotel Room, also formed the basis of one segment of the German portmanteau film Unheimliche Geschichten (1919), Angústia de uma Alma (1950) (in which the missing person was the young woman's brother as opposed to her mother) and Into Thin Air (1955), starring Hitchcock's daughter Patricia Hitchcock.
The British Board of Film Censors, to avoid political controversy, would not allow the foreign villains to be specifically identified in the script as Germans.
The cricket-obsessed characters Charters and Caldicott were created especially for this movie and do not appear in the novel written by Ethel Lina White.
Alfred Hitchcock: Near the end of the movie at Victoria Station wearing a black coat and smoking a cigarette.