Santhan, a medical practitioner, is in love with his cousin Vimala, with whom his marriage is fixed. Vimala's father, a banker, died under mysterious circumstances. Santhan develops a medicine, which transforms a person into a monstrous creature when consumed. He also invents the formula that reverts the person back to their original self. Santhan keeps this invention a secret. After reading his uncle's diary, Santhan realises that other voracious directors of the bank are responsible for his death. Santhan plans revenge on them by utilising his invention.
