An inexperienced young woman (Joan Fontaine) meets aristocratic widower Maxim de Winter (Laurence Olivier) at the French Riviera and soon becomes the second Mrs. de Winter.

Maxim takes his new bride back to Manderley, his grand mansion by the sea in south-western England, dominated by its housekeeper Mrs. Danvers (Judith Anderson), a chilly individual who had been a close confidante of the first Mrs. De Winter—Rebecca—with whom she is clearly still obsessed. She has even preserved Rebecca’s grand bedroom suite unchanged and continues to display various items that carry her monogram.

Eventually, her constant reminders of Rebecca’s glamour and sophistication convince the new Mrs. de Winter that Maxim is still in love with his first wife, which could explain his irrational outbursts of anger. She tries to please her husband by holding a costume party like he and Rebecca used to. Danvers advises her to copy the dress that one of Maxim’s ancestors is seen wearing in a portrait. Nevertheless, when she appears in the costume, Maxim is appalled since Rebecca had worn an identical dress at her last ball, just before her death.

Mrs. de Winter confronts Danvers about this but Danvers tells her she can never take Rebecca’s place and almost persuades her to jump to her death. At that moment, however the alarm is raised because a sunken boat has been found with Rebecca’s body in it.

Maxim now confesses to his new wife that his first marriage had been a sham from the start when Rebecca had declared that she had no intention of keeping to her vows but would just pretend to be the perfect wife and hostess for the sake of appearances. When she claimed she was pregnant by another man, she taunted Maxim that the estate might pass to someone other than Maxim’s line. During a heated argument, she fell, struck her head and died. To conceal the truth, Maxim took the body out in a boat, which he then scuttled and identified another body as Rebecca’s.

The sudden crisis causes the second Mrs. de Winter to shed her naïve ways as they both plan how to prove Maxim’s innocence. When the police claim the possibility of suicide, Rebecca’s lover Jack Favell attempts to blackmail Maxim by threatening to reveal that she had never been suicidal. When Maxim goes to the police, they suspect him of murder. However, further investigation reveals that she was not pregnant but terminally ill due to cancer, so the suicide verdict stands. Maxim realizes that Rebecca had been trying to goad him into killing her via indirect suicide, so that Maxim would be ruined.

A free man, Maxim returns home to see Manderley on fire, set ablaze by the deranged Mrs. Danvers. All escape except Danvers, when the ceiling collapses on her. The film ends with an R-monogrammed nightdress-case consumed by flames.