In 1959, Alfred Hitchcock opens his latest film, North by Northwest, to considerable success, but is troubled by a reporter's insinuation that it is time to retire. Seeking to reclaim the artistic daring of his youth, Alfred turns down film proposals like adapting Casino Royale in favor of a lurid horror novel called Psycho by Robert Bloch, which is based on the crimes of the serial killer, Ed Gein.
Alfred's wife and artistic collaborator, Alma, is no more enthusiastic about the idea than his appalled colleagues, especially since she is being lobbied by their writer friend, Whitfield Cook, to look at his own screenplay. However, she warms to Alfred's proposal, suggesting the innovative plot turn of killing the female lead early in the film. The studio heads prove more difficult to persuade, forcing Alfred to finance the film personally and use his Alfred Hitchcock Presents television crew to produce the film.
However, the pressures of this self-financed production, such as dealing with Geoffrey Shurlock of the Motion Picture Production Code, and Hitchcock's notorious lecherous habits, such as when they confer with the female lead, Janet Leigh, annoy Alma beyond endurance. To find a release, Alma begins a personal writing collaboration with Whitfield on his screenplay at his beach house without Alfred's knowledge. Alfred eventually discovers his wife's activity and suspects of her of having an affair. This concern affects Alfred's work on the film, such as giving Psycho's famous shower scene particularly ferocious ambiance even as he imagines Gein speaking to him.
Despite this tension, Alma's loyalty is such that she personally takes over production of his film when Alfred is temporarily bedridden after collapsing from overwork. Despite this, Alfred eventually confronts Alma and questions her activities with Whitfield. Alma, profoundly insulted at being accused of adultery after all her work with her husband, angrily denies it and their marriage is badly shaken.
Events take a turn for the worst with Alfred's rough cut of Psycho being poorly received by the studio executives while Alma discovers Whitfield philandering with a younger woman at his beach house. With both feeling chastened by these developments, Alfred and Alma reconcile and set to work on improving the film. Their renewed collaboration yields results, culminating in Alma convincing Alfred to accept their composer's suggestion for adding the famous harsh strings score for the shower scene, making it a bracingly effective moment of cinematic horror.
After maneuvering Shurlock into leaving the film's content largely intact, Alfred learns that the studio is only going to exhibit the film in a handful of theaters with minimal marketing. To compensate, Alfred arranges for special theater instructions to pique the public's interest in the film such as forbidding admittance after the film begins. At the film's premiere, Alfred waits in the lobby for the audience's reaction and is rewarded with a raucously enthusiastic reception.
With the film's screening being so well received, Alfred publicly thanks his wife afterward for helping make it possible and they affirm their love. At the conclusion at his home, Alfred addresses the audience noting Psycho proved a major high point of his artistic career and he is currently pondering his next project. At that, a crow lands on his shoulder as a reference to his successful follow-up effort, The Birds, before turning to meet with his wife
