Farz (1967)

When Criminal Investigating Officer, Amarnath is murdered during the line of duty; Intelligence suspect it is the handiwork of foreign criminals who wants to destroy India with the help of some Indian traitors thus secret agent, Gopal is sent down to investigate. Gopal does manages to find a lead in this case and work together with the help of Amarnath's sister, Kamla in locating some incriminating photographs that clearly shows a car registration number. He meets and fall in love with Sunita who then introduces him to her dad, Damodar. Gopal also find out that Damodar is a mere pawn in the hands of the same criminals he is looking for and must continue his investigation to reach the mastermind.