Who Killed Aunt Maggie?

New York radio advertising man Kirk Pierce quarrels with his fiancée, Sally Ambler, on their wedding day over a radio play she has written and wants him to submit to businessman Carter. Kirk states that her story, which revolves around a mansion's mysterious secret room, is ridiculous, and his criticism prompts Sally to break their engagement. Sally then receives a telegram from a friend, Bob Dunbar, stating that her great uncle Charlie is dying and her aunt Maggie wishes her to return to her childhood home of Wistaria Hall in Atlanta. After Sally leaves, Kirk receives a phone call from Dr. George Benedict, the husband of Sally's cousin Eve, who tells him that Sally will be in grave danger if she comes home. While the message stirs Kirk to follow Sally, she arrives home and finds the Ambler family distressed over Charlie's death. Maggie sends Sally to Charlie's room to pay her respects, but Sally discovers that his corpse is missing. Eve believes that it has disappeared, as an autopsy had revealed that Charlie was murdered. Meanwhile, Maggie, who is Charlie's sole heir, maintains that there is a secret room containing a priceless jade collection somewhere on the grounds. Kirk arrives, and Sally introduces him to the family. He learns from Benedict that Sally is next in line for the inheritance, after which Kirk uncovers an ancient diary that Maggie believes will provide a clue to the secret room's location. Kirk ridicules the idea but is forced to stay at the mansion after a storm makes the roads impassable and the phone lines are mysteriously cut. The family finds a strange intruder, who claims that he is John Lloyd, a tombstone representative, and that he has been injured in a car crash. While Lloyd skulks about the house, Sally discovers that Maggie has been murdered. Kirk and Bob repair the telephone lines and summon Sheriff Gregory, coroner Dodson, and troopers Leroy and Curtis. Dodson announces that Maggie was strangled with a woman's stocking and begins an investigation. The next morning, Sally learns that the real John Lloyd is at work in his company's office, while Eve finds the secret room. Soon after, however, she is found murdered in Maggie's room, from which Maggie's corpse has disappeared. While the family's hysteria grows, Sally accidentally finds the secret room as she searches for Maggie's cat, "Yahoody." In the cellar-like room, Sally is accosted by Benedict, who reveals that he killed Charlie for investigating his shady past, then Maggie and Eve when they discovered the room. Sally's cousin, Cynthia Lou, inadvertently reveals the garden entrance to the room, and Kirk descends the stairway with Andrew the butler. They find the missing bodies and arrive just as Benedict is about to kill Sally. Benedict escapes, but is captured by the man impersonating Lloyd, who is really John Cartigan, a private detective investigating Benedict. Cartigan reveals that Benedict is also wanted for murder in Chicago, and they leave with Gregory. Back in New York, Sally and Kirk fight over turning their adventures into a radio story, but their enterprising friends get a minister to marry them in the midst of their quarrel. The newlyweds then make up as Carter announces that he will sponsor their show.