The plot opens with Sathyam, an Assistant Police Commissioner rescuing a hooligan from encountering thirsty cops around the Napier Bridge in Chennai, only to arrest him later. He reminds his fellow cops that a cop's duty is to kill crime, not criminals. Sathyam meets his first challenge in tracking a mysterious killer of three ministers. In the process, he finds the culprit named Manicka Vel, only to receive a rude shock to know his identity. The murderer is none other than a former police officer based in Madurai, who inspired Sathyam to become an honest police officer. Revealing the reason behind his change of mind, the ex-cop says that he is on a killing spree as he failed to set the right things in khakhi uniform. Sathyam, who throws a challenge at his mentor that he would use the power of law to put the wrongdoers behind the bars, vows to throw light on the illegal activities of the Home minister Kondal Dasan, who aims for Tamil Nadu's Chief Minister post. In the meantime, he also has a romantic episode with Deivanayaki alias Deiva, a TV journalist. This begins with Deivanayaki suing the locality's children through their parents. The children swear vengeance through a 'gang leader' who happens to be none other than Sathyam himself. The 'gang' succeeds by making their rival a laughing stock with multiple pranks. Annoyance turns to love as Deiva and Sathyam get to know each other better. During his attempts to establish the truth, Sathyam faces various troubles. The Minister's proxies give him various troubles by killing children by offering them ice creams laced with drugs to eat and killing his mother. When Sathyam arrests Acharya, the Minister's proxy, and takes him to court, the Minister's henchmen attack him while driving and Sathyam is stabbed. Thillanayagam, the other proxy, shoots Acharya and blames Sathyam. Sathyam performs his mother's funeral rites and is suspended from the force and jailed. Manicka Vel, to be released the next day, feels sad for Sathyam and laments his loss in jail. Thillanayagam runs for MLA with the Minister's support so that he cannot be harmed by Sathyam. He gloats to Sathyam at the jail about his newfound power and challenges Sathyam's honour and dignity. At a public rally for Thillanayagam's candidature, the Kondal Dasan openly challenges and insults Sathyam, who is released from jail by a sympathetic officer and coming to disrupt the public rally. Manicka Vel stands in the corner aiming to kill Thillanayagam and Dasan. Sathyam arrives and exposes the Minister and Thillanayagam by shooting them and forcing them to confess the truth about the Minister's intentions and the death of the proxy. Thillanayagam reveals everything about himself, Acharya, and Dasan. While lamenting the situation he is in and calling for reform, Sathyam is shot by the Minister's henchman and questions the honesty and trust his people and fellow officers have in him. Manicka Vel arrives on the scene and salutes Sathyam, with other officers following suit. A newscast is shown with Kondal Dasan and Thillanayagam being arrested and Sathyam is reinstated in the police force. Sathyam is promoted to Deputy Commissioner by the Chief Minister and marries Deivanayaki, and the credits roll.