Secret Beyond the Door... (1948) is a psychological thriller and modern updating of the Bluebeard fairytale, directed by Fritz Lang, produced by Lang's Diana Productions, and released by Universal Pictures. The black-and-white film noir drama is about a woman who suspects her new rich architect husband has plans to eventually kill her.

In this Freudian version of the Bluebeard tale, a young, trust-funded New Yorker goes to Mexico on vacation before marrying an old friend whom she considers a safe choice for a husband. However, there she finds her dream man -- a handsome, mysterious stranger who spots her in a crowd. In a matter of days they marry, honeymoon and move to his mansion, to which he has added a wing full of rooms where famous murders took place. She discovers many secrets about the house and her husband, but what she really wants to know is what is in the room her husband always keeps locked. Written by Julie van Arcken