Gerald Meldrick  and Anya von Duren  are a pair of rival jewel thieves at large in India. Both parties are after the same prize, a priceless diamond owned by the Duchess of Beltravers . To inveigle their way into the Duchess' confidence, Gerald poses as a Scotland Yard detective, while Anya pretends to be an aristocrat. After working at cross purposes, they decide to team up, keeping one step ahead of a diligent police inspector  and mercenary freighter captain Chang . Both Gerald  and Anya betray the nobler sides of their natures in the end, fighting in a pitched battle in China against the invading Japanese army.