Nagin [English translation: Female Snake] is a 1976 Hindi horror fantasy thriller film produced and directed by Rajkumar Kohli. It features a huge ensemble cast including Sunil Dutt, Reena Roy, Jeetendra, Feroz Khan, Sanjay Khan, Vinod Mehra, Kabir Bedi, Rekha, Yogeeta Bali and Mumtaz. The film became a "superhit" at the box office.
The film was later remade in Telugu as Devathalara Deevinchandi  with Jayamalini in the "Nagin" role. It was also remade in Tamil with Sripriya playing the "Nagin" role in the film Neeya.
According to a myth, when snakes are of certain age, they can assume human form. Thus, the film begins with a male and a female in their human forms, singing and dancing amorously with each other. When the male turns back into a snake, he is shot by a member of a hunting party, who thought the snake was going to attack the woman. The rest of the story deals with the female taking revenge on the group of friends responsible for her lovers death.
Source : Nagin Wiki Page