Elaan (1971)

Naresh Kumar Saxena lives with his widowed mom and sister, Seema. He works as a freelance photographer and journalist. One day he meets with Mala Mehta and her dad, who is the Editor of a Newspaper. Mr. Mehta hires Naresh and assigns him to go to a remote island to investigate and expose some illegal activities there. Naresh goes there in the company of his friend, Shyam. Unfortunately, Naresh is caught by the island guards and lodged in a cell along with two others, one a scientist and Ram Singh, a hoodlum. The scientist confides in Naresh that he has invented an atomic ring that when inserted in someone's mouth will turn that person invisible, and subsequently passes away. Naresh puts the ring in his mouth, takes off his clothes, turns invisible and escapes.