Vijay is a Tamil professor living with his widowed mother and his sister Shanti. He is in love with Uma, who is a lawyer. During a visit to his friend Ravi's house, he is disgusted by the goings-on in his neighbourhood. 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 corruption's payroll and manages to warn them before making a raid. When Ravi's sister is killed and the perpetrator Mohanraj 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.

Mohanraj and his goons barges into Vijay's house where they assault Shanti and his mother and throw them from the terrace. Vijay then turns into a vigilante, walking the streets at nights and dealing out his own brand of justice – shoot first and ask questions latter to the gangsters. He soon becomes known as Robin Hood, helper of the poor and the police sends Singaaram, a CID officer, to unmask Robin Hood. Vijay kills Mohanraj and his uncle, after which he surrenders to Singaram revealing the truth, but Singaram mentions that he has already found the truth and decided not to arrest Vijay as he destroy the weeds that are harmful to the society. But Vijay feels guilty for his murders and surrenders himself. Uma appears in court in favour of Vijay and argues.

The day before the judgment, Singaram masks as a criminal and tries to molest the judge's daughter, seeing which the judge tries to shoot the criminal. Singaram reveals his identity and mentions that his intention was to make the judge understand that Vijay was also under a similar situation before. The judge sentences Vijay for lifetime imprisonment, but recommends to the president of India for granting a pardon.