A corrupt assistant of an equally corrupt mayor murders his boss and hides the body in a freezer. He finds a look-alike and forces him to pretend to be the mayor. The young man has a different agenda.

Vijay, a cop, is on a mission to apprehend Bhoopathy, a notorious criminal. He infiltrates the gang to become his right hand man. But, in the bargain, he ends up witnessing the killing of his mentor.

Vasu (Ajith Kumar) is a happy-go-lucky final-year college student who is forced to contest elections in the college after being persuaded by his friends Arun (Nithin Sathya) and Venkat Prabhu. He incurs the wrath of the local MLA Varadharajan (Charan Raj), whose son is studying in the same college and is also contesting the elections.
In the course of events, Varadharajan’s gang attacks Vasu and his friends. Vasu’s father Seenu (Vijayakumar), a tea shop owner, advises the students to take a plunge in politics and teach bad apples like Varadharajan a lesson. Taking cue from his words, Vasu does take the plunge in politics with the backing of college students and files a nomination for the assembly election in Kumbakonam constituency. Varadharajan is annoyed and angry at Vasu’s presumptuousness and tells him to back off from the elections. But Vasu goes ahead with his plans. The rest is a sequence of events by which Vasu wins the admiration of masses and succeeds in getting elected as MLA.

Shanmugham (Jeevan) comes to Chennai with his mother in search of his father (Raj Kapoor). When they get to the place, they see him living with another wife. In a hussle, he kills this old wife and sends this boy outside to beg. He comes out with dead mother and an auto driver (Chandrasekar) helps with all he has to cremate the body and gives some money and asks him to go back to his own city. Shanmugham wanted to read and become a great man. But he gets caught with the corrupt police guys and was used for their jobs (which involved murder). So when he grows up, he becomes a big rowdy by the name of Thotta (bullet). The highly corrupt police officer DCP Murugavel (Sampath Kumar) also uses him for a lot of encounters for which he takes credit and gets promoted to commissioner level. In one incident where he is asked to put acid on a girl Nalina’s (Priyamani) face, he finds that girl to be the auto driver’s daughter itself in her house. He helps that family, which is in poverty, with lot of gifts and also loves her. Nalina’s aim is to become a police officer and she tells this to Shanmugham. As he has commissioner influence, he promises to get her the job. For this he kills a minister who is a big rival of the chief minister (Livingston) at the instance of Murugavel. But when Nalina goes to Murugavel for the job, the latter insists that she have sex with him. When Shanmugham finds out what happened, he and Murugavel part ways. Shanmugham has a friend Giri, who is also a rowdy, but gets him married to a nice girl Gauri (Mallika). She wants to separate him from this rowdy group and get settled, for which she tries not to send him for their encounters. After much thought, Shanmugham lets them go separately. But Murugavel kills Giri in an encounter. Prabhakar (Saranraj), a CBI officer, wants to get Shanmugham alive, whereas Murugavel wants him killed, otherwise he would be in deep trouble as he was the one who made Shanmugham a rowdy after all. How Shanmugham overpowers