Shalimar (1978)

Kumar, a professional thief, crashes a gathering on Sir John Locksley's private island by pretending to be Raja Bahadur Singh's son. The other guests—K.P.W. Iyengar, Dr. Dubari, Colonel Columbus, and Countess Sylvia Rasmussen—are all master criminals, and Kumar's cover is immediately blown. Yet Sir John, terminally ill with cancer, lets him stay. His real purpose: find a worthy successor among them. To test them, he dares them to steal the Shalimar, a ruby worth 135 crores, from a heavily guarded, alarmed vault. Failure means death. Kumar is now trapped in a deadly game.