Mathimaran is a police constable who only reports to work and goes home daily without contributing anything useful to the society as his boss, Inspector Sathyamurthy, does not want to get on the wrong side of the upper levels of the police, who are corrupt and politically influenced, and is also unwilling to rock the present system due to past experience. Mathimaran and his fellow policemen never get any cases as a result, much to his irritation.

Mathimaran falls in love with Divya, who works as a nurse in a hospital, but hides his occupation from her as her family hates police officers. With her help, he finds out about an illegal organ donation racket orchestrated by a politician named Durai Arasan and Dr. Devasagayam, who is the chairman of the hospital where Divya works. They capture sick and injured migrant workers from North India, make them brain dead by administering them carbon monoxide instead of oxygen, and then harvest their organs, which they sell abroad for huge amounts of money. The organ donation scam gives Mathimaran his first real case, and he takes it on with enthusiasm after Sathyamurthy and Durai's estranged father Singaperumal, who had threatened to expose his son's misdeeds, are killed in a bomb blast orchestrated by Durai.

Mathimaran first confronts Devasagayam, who commits suicide, but not before admitting his role in the scam and giving detailed information about it. He then decides to confront Durai and get him arrested, but problem is that there is not enough evidence against Durai except Devasagayam's word, and Devasagayam is dead. He tries to get more information about Durai's role in the scam incognito. Unfortunately, Durai soon finds out that Mathimaran is after him, and a cat-and-mouse game begins between the two. In the process, Mathimaran is suspended from duty, as the police commissioner is close to Durai. Undaunted, he manages to expose the scam and Durai's involvement in it to the media, but Durai wriggles out of arrest.

Mathimaran decides to finish off Durai to end the scam once and for all. He creates a ruckus during a felicitation function for Durai. In the chaos that ensues, he shoots Durai in the leg and gives him the same treatment which had been meted out to the North Indian workers: administering him carbon monoxide and then harvesting his organs after he is declared brain dead. Durai's death is covered up as a terrorist attack. Mathimaran is eventually promoted to Inspector in reward for his efforts in thwarting the organ donation scam. He also gets accepted by Divya's family, despite being a police officer, and marries Divya.