From the Universal synopsis: Retired Inspector Blake of Scotland Yard learns that Lord Blanton has acquired the sacred "Love Ring"---a cursed jewel that has brought grief to its previous owners. Prince Darius seeks to obtain the ring, and the mummy of a princess of an ancient country to return them to his homeland. Blake and his servant, Jarvis, find a card---The Queen of Diamonds---which is the mark of the most dangerous woman in the underworld. Mary Duveen , the Blanton housekeeper, is really the Queen, disguising herself as a spectacularly ugly crone. Darius comes to believe that Lady Diana Blanton, Lord Blanton`s daughter, is the reincarnation of Princess Xah Fari, and sets his sights on her also. His hypnotic influence soon has the girl experiencing dreams of a vanished civilization. Mary acquires the ring and Jarvis recovers it and Mary steals it back and plants it on Lady Di, and then lures her to a Limehouse den but Blake and Jarvis follow and rescue her and the ring.