Marudhamalai (Arjun), goes to work as Constable in the town of Nachiapuram after passing his police training by getting a merit selection. Here he meets 'Encounter' Ekambaram (Vadivelu), his senior officer. He is asked to do all sorts of petty work for him, and one day, Marudhamalai loses a convict on the way to the court due to Ekambaram's soft heart. He then is to clean the floors of the inspector's house, and there he falls in love with Divya (Meera). Then, later in the market, after Ekambaram is humiliated by a beggar, Marudhamalai sees Maasi (Lal), the 'boss' of the city, killing a person who stood for a candidate in the elections. That constituency has not had an MLA for the last 16 years due to Maasi. Maasi's caste people have been 70% majority in that Nachiyarpuram MLA constituency, but the Government named the constituency as a Reserved Constituency 16 years ago. Since then, Maasi either postpones the MLA election by murdering a candidate or makes sure that his house servant from a lower caste is elected as MLA and then resigns immediately to cause a vacancy of the office. Since Maasi has his caste's support and heavy income, the Government has kept ignoring him.

Then the Chief election commissioner SuryaNarayanan IAS comes to the town. He meets and challenges Maasi to stop him from holding by-elections in that area. Then, during the election day, despite a lot of security, Maasi's men, with the help of a man who acts as a guard, come and drive away from the people who came for voting and are about to kill the commissioner, when Marudhamalai's father (Nassar) slaps Maasi for creating violence. At that time, Marudhamalai comes, beats up Maasi's men, and humiliates Maasi in front of all the people by handcuffing him with his dhoti. Maasi is then arrested and sentenced for 15 days imprisonment without bail.

For his bravery, Marudhamalai is initially suspended, but then promoted to the inspector of the station. With 12 days remaining in Maasi's imprisonment, Marudhamalai seals off his illegal sources of income, and arrests Maasi's henchmen for choking his empire. To exact revenge, Maasi's brother kills Marudhamalai's father by car-bomb. Later, he kills Maasi's two brothers using various unofficial methods, and Maasi vows to kill him the day he is released. Later, as Maasi is released, Marudhamalai gets an order to kill him. He fights the men single-handedly and kills them all, proving his bravery. Marudhamalai is further promoted as DSP.