Warner Brothers insisted on shooting the movie in 3-D although the craze was fading and Alfred Hitchcock was sure the movie would be released flat. The director wanted the first shot to be that of a close-up of a finger dialing the letter M on a rotary dial telephone, but the 3-D camera would not be able to focus such a close-up correctly. Hitchcock ordered a giant finger made from wood with a proportionally large dial built in order to achieve the effect.
During the attack scene according to the script, Grace Kelly was to get out of bed, put her robe on, and answer the phone when it rang. Grace Kelly contended that no woman, being at home, would put a robe on to answer the phone. Alfred Hitchcock agreed, and so the scene was shot with her in her nightgown.
Alfred Hitchcock had chosen a very expensive robe for Grace Kelly to wear when she answered the phone. The actress balked and said that no woman would put on such a robe, just to answer the ringing telephone while she was asleep alone, but would answer it in her slip. Hitchcock agreed to do it her way and liked the way the rushes turned out. The director agreed to allow the actress to make all costume decisions for herself in their subsequent films together, afterwards.
Filmed in 3-D, which explains the prevalence of low-angle shots with lamps and other objects between the audience and the cast members. There was only a brief original release in 3-D, followed by a conventional, "flat" release; The New York Times review mentioned it opened with the "flat" release at the Paramount in New York. The 3-D version was re-issued in 1980.
At their first meeting, the untrustworthy Captain Swann is wearing a tie the colors of a Guards regimental tie. However this is not a genuine tie, as the diagonal stripes run in the American direction, opposite to British style. This is a contemporary detail, used by spivs.* The tie resembles the trustworthy Guards tie well enough to fool most, but gives an excuse if a genuine Guardsman queries one's service record. (*"Spiv" is a Britishism for "a man who lives by his wits without regular employment" [Merriam-Webster's Collegiate Dictionary, eleventh edition].)
Alfred Hitchcock lost close to twenty pounds due to nervous anxiety when filming the scissors murder scene. He obsessively rehearsed the scene and shot take after take in order to get capture the scene the way he had envisioned it.
Adapted from a Broadway play that opened at the Plymouth Theater in New York on Wednesday, October 29th, 1952, and ran for 552 performances. In the original production, Maurice Evans played Tony Wendice. In this film, John Williams and Anthony Dawson re-created their stage roles of Chief Inspector Hubbard and Captain Lesgate. J. Pat O'Malley later replaced Williams as Hubbard.
In a television interview Ray Milland said that he had fluffed his lines in a particular scene in the movie and ruefully apologized to the director. Alfred Hitchcock, he said, stared at him stonily for few seconds and then said: "I wound it up, put it on the floor, and it wouldn't go."
Alfred Hitchcock made a special effort to shoot scenes indoors, almost exclusively. Only a few brief shots, usually involving Chief Inspector Hubbard, take place outside. Hitchcock believed the decision to shoot most scenes indoors would create a sense of claustrophobia.
Warner Brothers forced Alfred Hitchcock to make the movie to fulfill his contract - such was his disinterest that he claimed he could have phoned in his direction, and that the action wouldn't have been any less interesting if he'd staged it in a phone booth.
A portion of the scene where Wendice is explaining the details of the murder plan to Swann is shot at a downward angle. Swann is standing at the garden door and Wendice is slowly pacing from Swann to the hall door. The lighting used casts strong shadows of Wendice as he walks. Near the end of the scene, Wendice stops near Swann and his shadow could easily pass for that of Hitchcock.
The trivia items below may give away important plot points.
After several unsuccessful attempts to film the scene where Margot stabs Swan with the scissors, Alfred Hitchcock said, "This is nicely done but there wasn't enough gleam to the scissors, and a murder without gleaming scissors is like asparagus without the hollandaise sauce - tasteless."
As several of Alfred Hitchcock films carry a MacGuffin (a plot device that motivates the character and advances the story but has a little relevance to the film itself) in this film the MacGuffin itself is the latchkey.