It is set in coastal Cornwall in the early 19th century. Phillip Ashley (Burton) is a callow youth who has grown up in the lap of luxury, as the ward of his uncle Ambrose. When Phillip is in his early 20s uncle Ambrose goes to the warmer climates of Italy to restore his health. From there he sends Phillip a letter telling him that he is getting married to a woman named Rachel Sangaletti, the widow of an Italian count.
Phillip is disappointed to read that his uncle's return home is delayed but he grows even more concerned when more disturbing letters arrive. Written in an unsteady scrawl, they tell Phillip that Rachel and her lawyer friend Guido are conspiring to murder him. Phillip sets off for Florence but arrives to find that his uncle has already died and that Rachel has gone away. Guido brushes off Phillip's suspicions, telling him that the estate was left to him and not Rachel, and that Ambrose's accusations were the result of a brain tumor that left him mentally unbalanced.
Phillip returns home. Eventually his "cousin Rachel" (de Havilland) shows up for a surprise visit. She is beautiful and charming, and passionate Phillip soon finds himself falling in love with her and giving her a generous allowance from the estate. But soon events take a turn, Phillip finds himself ill for the first time in his life, and he starts to wonder if Ambrose was right after all.
Hollywood film debut and Star-Making Role for Burton, who had made a name for himself on the London stage but whose movie career had been only a few scattered parts in the British film industry. A movie comeback role for de Havilland, who had taken three years away from Hollywood to act on the stage.
- Betty and Veronica: There's Louise, daughter of Phillip's neighbor and estate trustee Nicholas, who is beautiful and seems a natural match for Phillip, but is also young and virginal—the Betty. Then there's Rachel, a good decade older than Phillip, darkly sensual, who apparently becomes his lover—the Veronica.
- Call-Back: In his last letter Ambrose calls his wife "Rachel my torment". Phillip uses the exact same line at the end of the film to describe her.
- The Disease That Shall Not Be Named: Ambrose's father died of a tumor in the brain, and Rachel and Guido attribute both Ambrose's death and the terrifying letters he sent to Phillip to a tumor in his brain that affected his mental state. The word "cancer" is not used.
- The Film of the Book: A highly faithful adaptation of a novel by Daphne Du Maurier.
- If I Can't Have You...: "Never leave me, you understand?", says Phillip to Rachel, right after he's done strangling her for a little bit.
- Letting Her Hair Down: Rachel has her hair all done up in sort of a proto-version of the Princess Leia bun. So it makes a dramatic moment when she comes into Phillip's bedroom for the first time, her long hair cascading down her shoulders, and kisses him.
- A Minor Kidroduction: A couple of scenes establishing Phillip as a child in the care of his uncle Ambrose before the story proper starts with Ambrose going off to Italy and leaving adult Phillip behind.
- Murder by Inaction: Rachel says she's going to be walking along a route that Phillip knows to be dangerously unsafe, because the carpenter told him the bridge has not been finished yet. He doesn't say anything. She falls to her death.
- Sexy Discretion Shot: The film cuts away after Rachel and Phillip kiss on the floor of her room.
- Title Drop: Phillip swears a vow that he will repay "my cousin Rachel."
- The Un-Reveal: We never do find out if Rachel really did kill her husband and whether or not she was poisoning Phillip. Phillip's last line of dialogue has him saying "Were you innocent, or were you guilty? Rachel my torment."
- Widow's Weeds: Rachel is fully done up in black dress and veil when she arrives at the estate and remains so for some time afterwards.