Thorold Dickinson's classic thriller stars Anton Walbrook as Paul Mallen, who moves into a London townhouse with his new bride Bella. Her family has a history of mental instability and when objects go missing without reason and when she claims the gaslight dims of its own accord, he suggests she is beginning to lose her mind. But ex-policeman B G Rough, who now works as a ostler, recognises Mallen as the nephew of a woman brutally murdered in the very house he and his wife now live in and, what's more, a house which still harbours a fortune in rubies which the killer never found. Could Mallen be somehow connected to the crime and is the parlour maid Nancy, who is no better than she should be, a conspirator in her master's plans?