This suspenseful crime saga follows the twists and turns in the life of Sakthi (Vijay) is the adopted son of a Madurai-based don Sivan (Mohanlal) and is also his right-hand man, bodyguard and driver. He 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 (brown colour, which is worn by policemen in India), constantly teases his friend Gopal (Soori), who is a Sub-inspector and even loses romantic interest on a woman named Shanthi (Kajal Aggarwal) after he finds out that she is a police inspector.
However, when Sivan is insulted by the new Police Commissioner of Madurai (Pradeep Rawat), he forces Sakthi to become a police officer to save his crime syndicate and prove the Commissioner's words wrong (A policeman can think like a criminal, but a criminal can never think like a policeman). Reluctantly taking charge as Assistant Commissioner of Police, Sakthi 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.
This incident, compounded by the assault of a woman (Meenal), whose husband was killed in the gas leak, by Sivan's henchmen when she had come to the police station to lodge a complaint against Sivan, causes Sakthi to take up the path of a honest and upright police officer. Sakthi's new persona is not liked by Sivan and after a heated argument between the two, he disowns Sakthi. A cat-and-mouse game then begins between Sivan and Sakthi, with Sivan, his henchmen and his family determined to humiliate Sakthi at every opportunity, while Sakthi, assisted by Shanthi and Gopal, tries to rid Madurai of Sivan's influence. Sakthi is soon promoted to Deputy Commissioner of Police for his efforts.
Later, Sakthi finds out that Sivan's other adopted son, a minister Aadhi Kesavan aka Aadhi (Sampath Raj) is plotting to kill Sivan in revenge for Sivan killing his police officer father (the same police officer who killed Sakthi's father) in his childhood. Since Sakthi had inadvertently thwarted his earlier plans to kill Sivan, he also plans to get Sakthi killed at the hands of Sivan by killing Sivan's son Vignesh (Mahat Raghavendra) and putting the blame on Sakthi for Vignesh's death. Unfortunately for Aadhi, Sivan sees through his plan and reconciles with Sakthi, both of whom team up to kill Aadhi. Sakthi then reluctantly arrests a reformed Sivan for his misdeeds, on Sivan's request.