A series of murders take place in the district of Avadi in the same pattern; stabbing by a knife. Each time the victim is paralysed before being killed. Police suspect several people and they narrow down the killer by his age, which should be more than 70 years with the writing style based on the letter left behind by the killer while murdering his recent victim, an officer in the government treasury. The officer is killed by an old man who is later known to be Senapathy, a veteran Indian freedom fighter, for demanding a bribe to do his duty i.e threatening a poor old woman to bribe him to hand over compensation amount of Rs.10,000 given by the government as her husband got killed in a riot.

Chandra Bose a.k.a. Chandru (Kamal Haasan) is a small-time middle man stationed outside Regional Transport Office, who aids people in greasing the right officials inside the RTO for getting permits and licenses. His assistant Subbaiah (Goundamani), and Paneerselvam (Senthil), an RTO official, are engaged in regular tiffs while Aishwarya (Manisha Koirala), Chandru's love interest and an avid animal rights activist, also battle it out with Sapna (Urmila Matondkar), the daughter of an RTO official. Chandru is trying to hobnob to secure a job for himself at the RTO. Aishwarya is irked by the fact that Sapna (as well her mom) is exploiting Chandru's situation and gets him to do grocery shopping, laundry, and almost every household chore.

Meanwhile, Krishnaswamy (Nedumudi Venu), a Bureau officer, manages to trace his way to Senapathy's (Kamal Haasan) house. Senapathy is Chandru's father. Archived newspaper reports say that Senapathy was a soldier in the Indian National Army, who was an extremist. Senapati's wife Amirthavalli (Sukanya) details the story on their struggles during pre-independence India, the discrimination by British officials and the Indian Freedom Movement Rebellions against the British atrocities, etc., leading Senapathy to marrying Amirthavalli, but leaving for Singapore to join Subhas Chandra Bose to be part of the INA. He returns after independence and unites with his wife.

In the present day, when Krishnaswamy tries to arrest Senapathy, he escapes with his expertise in Varma kalai. Senapathy then goes on to commit a murder in front of television audiences by killing a corrupt doctor (Nizhalgal Ravi), who refused to attend immediately to Senapathy's daughter Kasturi (Kasthuri), who was suffering from third degree burns because he insisted on a bribe, which Senapathy refused in the past, thus killing her. Chandru parts ways with his father because of his excessive insistence on honesty and righteousness, and he considers these values to be dead and worthless. Public support surges for the Indian as he exposes so many corrupt people. Senapathy does not do his son any favours either. Chandru had earlier taken a bribe and given a safety certificate to a bus with faulty brakes, which eventually killed 40 school children it was carrying, plus the driver operating it, and thus, Chandru is held responsible. Senapathy is bent on giving Chandru the same punishment as he gives others, i.e., death. Despite pleas from Amirthvalli and Aishwarya to spare Chandru's life, Senapathy heads for the airport where Chandru is attempting to flee to Mumbai. A chase then culminates at the airport, where Senapathy kills Chandru and apparently dies in an explosion. However, Krishnaswamy discovers that Senapathy escaped moments before the jeep exploded, which killed his son while investigating the television footage at the airport.

The epilogue shows Senapathy calling Krishnaswamy from a foreign land (Hong Kong), indicating that he will be back should the need for him arise.