The city of Chennai is rife with the nefarious activities of land mafia. There are two rival gangs; one under Ali Bhai (Prakash Raj), who resides in Dubai and controls his India operations through his brothers Guru (Vincent Asokan) and Logu (Subbaraju) as well as his girlfriend Mona (Brinda Parekh); and another operated by a local goon Narasimhan (Anandaraj). They threaten builders and land owners into giving them protection money or property, through force, extortion or murder. Mohammed Maideen Khan (Napoleon) takes charge as the new Police Commissioner of Chennai and starts cracking down on crime.
Tamil (Vijay), a thug, is abducted by Logu and his henchmen. Tamil has taken a contract from Narasimhan to beat up Logu, which he does. However, Guru and Mona invite Tamil to join their gang. Tamil declines stating that he does not work for any gang, but is ready to do anything given enough money. Meanwhile, Tamil falls in love with Shruthi (Asin), when he visits his friend Saravanan’s (Sreeman) aerobics class, but she mistakes him for a thug. Shruthi, a college student, lives with her widowed mother Lakshmi (Sriranjani) and younger brother Pappu (Master Bharath). Body Soda (Vadivelu), a bogus Kung Fu master, lives above Shruthi’s house and frequently, albeit comically and unsuccessfully, tries to convince Shruthi to marry him. Inspector Govindan (Mukesh Tiwari) is a corrupt police inspector in the colony where Tamil and Shruthi live and is on the payroll of Ali Bhai. He lusts for Shruthi and decides to make her his mistress, even after she rejects him multiple times.
Tamil’s first assignment with Ali Bhai’s gang is to kill a member of Narasimhan’s gang. However, police show up at the spot where Tamil and the other gangsters are waiting. Tamil engages the cops long enough for the others to finish the task and flee. He also helps Shruthi escape from Govindan. She is impressed by his kindness and a friendship soon blossoms between the two, leading to the development of unspoken romantic feelings for each other. When Shruthi tries to express her feelings to Tamil, they are attacked by members of Narasimhan’s gang, whom Tamil finishes off. Shruthi is shocked to learn that Tamil is a gangster with no qualms about killing people.
Later, Govindan arranges for some thugs to pretend to rape Shruthi, so that no decent family will want to take her as their daughter-in-law, as a result of which with no other option Shruthi and Lakshmi will accept his demands. Tamil learns of this and thrashes Govindan incognito. After much ado and mental anguish, Shruthi accepts Tamil’s love.
Soon, Guru is found dead, presumably killed by Narasimhan in retaliation against the death of his gang members at the hands of Tamil earlier, which forces Ali Bhai to come to Chennai and kill Narasimhan. He also meets Tamil to discuss the killing of a minister by blowing up a school. Tamil disagrees with Ali Bhai’s method as it would involve killing innocents including women and children. In the middle of their argument, the police raid the club and arrest Ali Bhai. His gang members retaliate by kidnapping Mohammed’s daughter, drugging her and creating a lewd video of her which they threaten to release to the media if Ali Bhai is not released, forcing the embattled commissioner to release Ali Bhai. In her drugged state, Mohammed’s daughter also reveals that Mohammed had placed a mole in Ali Bhai’s gang. The gang members find out that a police officer by the name of Satyamoorthy, the son of a retired police inspector Shanmugavel (Nassar), has gone undercover to finish off the underworld mafia gangs and is now a part of their gang. Ali Bhai kills Satyamoorthy in front of Shanmugavel. However, it is revealed that the person who died was actually Saravanan, who was Shanmugavel’s adopted son. Ali Bhai then kills Shanmugavel, hoping that the real Satyamoorthy would come to see his father’s body and avenge his death. When the real Satyamoorthy actually turns up, everyone, especially Shruthi and Govindan, are shocked to see that he is revealed to be Tamil.
After the funerals of Shanmugavel and Saravanan, Satyamoorthy forces Govindan to call Ali Bhai to find out his location, which is Binny Mills. He goes there and starts to dispatch Ali Bhai’s men one by one, rescuing the commissioner’s daughter in the process. In a final confrontation, Satyamoorthy kills Ali Bhai by slashing his throat with a broken glass window, following which he utilizes his own gun and kills Govindan also.