Shakthi is the adopted son of a Madurai-based crime boss, Sivan and is also his right-hand man, bodyguard and driver. Sivan lives happily with Shakthi, his wife, his son and daughter Vignesh and Mahalaskhmi. Shakthi hates the police due to a police officer killing his father, who was Sivan's driver, in his childhood. His hatred is such that he hates the khaki colour (which is worn by policemen in India), constantly teases his friend Gopal, who gets selected as a constable, and even loses romantic interest on a woman named Shanthi after he finds out that she is a police inspector. However, when Sivan is insulted by Ajay Rathore, a newly appointed police commissioner of Madurai, he forces Shakthi to become an IPS officer to save his crime syndicate and prove the commissioner's words wrong.

Reluctantly taking charge as ACP of Madurai City East, Shakthi gives free rein to Sivan and his henchmen, who wreak havoc over Madurai, until one of their activities inadvertently causes a gas leak which destroys a school and some nearby buildings, killing several people, including women and children. The incident, along with the assault of a woman by Sivan's henchmen when she had come to the police station to lodge a complaint against Sivan for killing her husband, causes Shakthi to take up the path of an honest and upright police officer. He thrashes Sivan's henchmen who assaulted the woman. Shakthi's new persona is not liked by Sivan and after a heated argument between the two, he disowns Shakthi. A cat-and-mouse game then begins between Sivan and Shakthi, with Sivan and his henchmen, determined to humiliate Shakthi at every opportunity, while Shakthi, assisted by Shanthi and Gopal, tries to rid Sivan's influence in Madurai. Shakthi is soon promoted to ASP for his efforts.

Later, Shakthi finds out that Sivan's other adopted son, a minister Aadhi Kesavan is plotting to kill Sivan in revenge for Sivan killing his police officer father (the same police officer who killed Shakthi's father) in his childhood. Since Shakthi had inadvertently thwarted his earlier plans to kill Sivan, he also plans to get Shakthi killed at the hands of Sivan by killing Sivan's son Vignesh and putting the blame on Shakthi for Vignesh's death. Unfortunately for Aadhi, Sivan learns about his plan and reconciles with Shakti, where they fight Aadhi's henchmen and Aadhi. Shakthi beats up Aadhi and gives him to Sivan to kill. Sivan gives Aadhi a choice to kill himself. Aadhi takes up the choice and slits his throat thereby killing him. Shakthi reluctantly arrests a reformed Sivan for his misdeeds, on Sivan's request.