The stunt where the man crawled under the carousel was not done with trick photography. Alfred Hitchcock claimed that this was the most dangerous stunt ever performed under his direction, and would never allow it to be done again.
The film did not initially end with Guy Haines and Anne Morton on the train. In another version of the film it ends just before this. This other reel was mistakenly labeled 'the British version' leading people to believe that this was what was shown in Britain. This is in fact incorrect and the same ending was broadcast in Britain and America.
When the movie was released in Germany in 1952, about five minutes were removed which were considered too brutal or sadistic. Later the scenes were re-added for TV, but they are subtitled, while the rest of the movie is dubbed.
This is the movie that determined the location of Carol Burnett's star on the Hollywood Walk of Fame. In 1951, she was working as an usher when this film was playing at the Warner Theatre on Hollywood Blvd. A couple arrived late, and Burnett, having already seen the film, advised them that it was a wonderful film that should be seen from the very beginning. The manager of the theatre very rudely fired her for this. Years later, when Carol Burnett was asked where she would like to have her star placed on the Hollywood Walk of Fame, she requested that it be placed in front of that theatre.
Raymond Chandler seems to have gone out of his way to behave disagreeably to Alfred Hitchcock. When Hitchcock arrived at Chandler's home for a story meeting, Chandler hollered from his window, "Look at the fat bastard trying to get out of his car!"
As Guy leaves the last match, part of a quotation clearly including the words "two impostors" is visible on the beam above his head. It is from Rudyard Kipling's poem "If." The line reads "If you can meet with triumph and disaster / And treat those two impostors just the same..."
Alfred Hitchcock had admired Edgar Allan Poe's stories since his teenage years, and went on to put Edgar Allan Poe references in his films. French critics noticed that there are connections between the runaway carousel in this film and Poe's "A Descent into the Maelstrom".
In Farley Granger/Skip E. Lowe Interview, Farley Granger revealed that this film and They Live by Night (1948) were his favorite films. Farley Granger also revealed that he loved working with Robert Walker and was very upset when he heard about Robert Walker's sudden death which happened couple of months after the shooting of this film.
There were several changes made from the original novel: the character Bruno Antony was named Charles Anthony Bruno and Guy Haines was an architect, not a tennis player. Also, Anne Morton was originally named Anne Faulkner.