Secret Beyond the Door is a 1947 American film noir psychological thriller and a modern updating of the Bluebeard fairytale, directed by Fritz Lang, produced by Lang's Diana Productions, and released by Universal Pictures. The film stars Joan Bennett and was produced by her husband Walter Wanger. The black-and-white film noir drama is about a woman who suspects her new husband, an architect, plans to kill her.
Plot
Celia (Joan Bennett), a rich New York heiress, remembers on her wedding day how she refused all proposals in New York, came to Mexico for a vacation, and instantly fell in love with the architect Mark Lamphere (Michael Redgrave). They have a happy honeymoon until she playfully locks him out of their hotel room, at which point he turns unaccountably cold toward her, and suddenly leaves her to return to his New England home for what he says is business.
She follows him, and when she turns up at the large mansion which he designed and built, she discovers that he is actually a widower with a small son. This boy, David, is being looked after by Mark’s sister Caroline (Anne Revere) and his trusted secretary, Miss Robey (Barbara O’Neil), whose face was scarred saving David’s life in a fire and who wears a scarf to conceal the disfigurement. Celia makes friends with David easily, but is uneasy about Mark’s mood swings, especially when Caroline hints that he caused his first wife Eleanor’s death; was it by making it clear he did not love her after the birth of David so that she pined away, or worse? Caroline also tells of having to lock Mark in his room when he was a boy. Celia is even more uneasy when Mark displays to their party guests the suite of special rooms he has had built on a special gated corridor in the mansion. Each of the first six rooms is an exact reproduction of a famous murder scene, and there is a seventh room which is locked and which Mark refuses to show.
Celia, wondering if the seventh room shows the scene of Mark’s murder of Eleanor, cuts down one of their bedroom candles to soften the wax and make a wax impression of the room’s key. While doing this, she catches Miss Robey without her concealing scarf, and learns that she had plastic surgery and her face is perfect again. She was pretending to be still disfigured to keep Mark and Caroline's gratitude for saving David and avoid being fired from her job, and she was hoping to marry Mark herself until Celia turned up. Celia promises not to tell on her.
Mark is disturbed at the unequal height of the two candles in the bedroom. Celia receives the copy of the key she had made to the seventh room, enters it and recognizes it as an exact duplicate of her and Mark’s bedroom. She concludes that it does indeed commemorate the death of Eleanor until she notices that the dresser candles are uneven in the same way they are in the real bedroom now. The room is to display not Mark’s past murder of Eleanor but his future murder of her. She runs away.
Mark has a daydream of being tried in a shadowy court, where he admits that he has a strong compulsion to kill Celia even though he loves her. He left her in Mexico to avoid doing this, but now the urge is back and he must leave her again. He dismisses Miss Robey for disloyalty, having noticed her deceit about her scar, and he and Caroline have a quarrel where she claims to be furious about having to run everything by herself and he is angry at her controlling him all her life.
Celia returns because she loves Mark, and he is alarmed because it means they will be alone in the house together. He tries to leave her again to save her life, but his compulsion overcomes him and he goes back. He finds Celia sitting waiting for him in the seventh room. She tells him she is there because she’d rather die than live without him. She channels the psychological theories advanced about murderers at the party (by a character billed only as “Intellectual Sub-Deb”), and begs him to remember what happened in his childhood to make him this way. And he does! When he was ten, his adored mother promised to read to him before she left to go dancing, but he found himself locked in his room as she departed. His pounding and screaming were in vain, and his love for his mother was transmuted into hate which was transferred to Celia when she locked the door of their honeymoon room. He advances on her to strangle her with a scarf. Celia reveals that it was Caroline, not their mother, who locked him in; he accepts this, and the scarf falls from his hand. They then notice smoke and fire; Miss Robey