The film's source was a novel by the French virtuoso team, Boileau and Narcejac.Although the psychological murder mystery had been written with the director in mind, he never intended to retain more than the basic plot line—and the erotic overtones.

When Hitchcock planned the film, he had Vera Miles mind for the female lead When she was unavailable, Hitchcock decided to hire one of America's favourite screen actresses, Kim Novak, to play the dual role of Madeleine/Judy. To emphasize the contrast between the two key women in the film, Novak's Madeleine was shot using only her right profile, while her Judy was seen in left profile.

Scottie Ferguson (James Stewart) is a former police detective who resigned from his job after a colleague fell to his death because of Scottie's fear of heights. Soon after, he is asked by a friend to shadow his wife, Madeleine, who seems to be contemplating suicide. Scottie falls in love with her, but is unable to save her from falling to her death—again because of his fear of heights.

Distraught, he tries to compensate by transforming another woman, Judy, into a facsimile of Madeleine—only to suspect that there is more than a physical resemblance between the two women. As is often the case with Hitchcock's work, the hero's weakness—in this case his acrophobia—is not so much physical as moral. More than a fear of heights, the vertigo he experiences is a symptom of his attraction towards the unknown, fearful yet beckoning Madeleine/Judy is a projection of fantasies and desires he vainly tries to control.

Stewart's star persona was so likeable that contemporary audiences and critics were unwilling to accept the story's "deep logic", which springs from the near-psychotic nature of the character he plays.

Hitchcock always felt the real suspense in the film was not the enigma of the two women, the complex cross references within the film's text are keyed to Scottie's emotional conflict, of which the "surface" mystery is merely a symptom.