Vijay (Rajinikanth) is a Tamil professor living with his widowed mother and his sister. He is in love with Uma (Ambika (actress)), a lawyer. During a visit to his friend Ravi's (Nizhalgal Ravi) house, he is disgusted by goings-on in his neighborhood. Illicit liquor is being sold at a tea-stall while prostitution is flourishing in another house in the same colony. But his complaints to the police, yield nothing since the policeman is on the villains' payroll and manages to warn them before making a raid. When Ravi's sister is raped and killed and the perpetrator Mohanraj (Sathyaraj) gets off scot-free with help from a minister, Vijay and Ravi take matters into their own hands and clean up the tea-stall and brothel on their own. Wanting to teach Vijay a lesson, Mohanraj and his goondas rape his sister (who then commits suicide) and kill his mother. Vijay then turns into a vigilante, walking the streets at nights and dealing out his own brand of justice - shoot first and ask questions later - to the rowdies and goondas. He soon becomes known as Robin Hood, helper of the poor and the police sends Singaaram (Bhagyaraj), a CID officer to unmask Robin Hood.