 In London, at Pimlico Square 12, the ancient lady Alice Barlow (Marie Wright) is brutally killed and her famous rubies miss. Because of the murder, the house stays empty for twenty years, when Paul Mallen (Anton Walbrook) and his sick wife Bella (Diana Wynyard) move to the place. Bella apparently had a nervous breakdown, having problems with her memory and becoming kleptomaniac. When the retired policeman B.G. Rough (Frank Pettingell) sees Paul Mallen on the street, he immediately recognizes him as being Louis Bauer, the nephew and killer of Alice Barlow. He decides to find evidences to prove that Paul and Louis are the same man, while Bella is being driven mad and menaced of being interned in an asylum by her husband.