A series of murders take place in Avadi, Chennai, in the same pattern; stabbing by a knife. Each time the victim is paralysed before being killed. Police, led by IPS officer Krishnaswamy, suspect several people and they narrow down the killer by his age, which should be more than 70 years based on the writing style of a 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 who was a member of the Indian National Army led by Subhas Chandra Bose, for threatening a poor old woman to bribe him to hand over compensation amount of ₹10,000 given by the government as her husband got killed in a riot.
Chandra Bose alias Chandru is a small-time broker stationed outside the Regional Transport Office at Chennai, who aids people in greasing the right officials inside the RTO for getting permits and licenses. His assistant Subbaiah, and Paneerselvam, an RTO official, are engaged in regular tiffs while Aishwarya, Chandru’s love interest and an avid animal rights activist, also battles it out with Sapna, a medical student and the daughter of an RTO official. Chandru hobnobs with Sapna and her family to secure a job as a brake inspector at the RTO. Aishwarya is irked by the fact that Sapna, as well as her mother, are exploiting Chandru’s situation, getting him to do grocery shopping, laundry, and almost every household chore. It is soon revealed that Chandru is none other than Senapathy’s son. They both had parted ways due to Senapathy’s excessive insistence on honesty and righteousness, which Chandru considers to be dead and worthless.
Meanwhile, Krishnaswamy manages to trace his way to Senapathy’s house. When he tries to arrest Senapathy, he and his wife Amirthavalli, a puppeteer, escape with his expertise in Varma kalai. Senapathy then goes on to commit a murder in front of television audiences by killing a corrupt doctor, who refused to treat Senapathy’s daughter Kasturi, who was suffering from third-degree burns, because he insisted on a bribe which Senapathy refused, thus killing her. Public support surges for Senapathy as he exposes so many corrupt people. Senapathy does not do his son any favours either. Chandru, who managed to bribe his way to a brake inspector job, takes a bribe and gives a safety certificate to a bus with faulty brakes, which eventually kills 40 school children it is carrying, plus the driver operating it. But, Chandru tries to put the blame on the bus driver for drunk driving and manages to bribe a police officer and a doctor on the same. 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 involving an aeroplane. However, Krishnaswamy, on investigating discovers that Senapathy escaped moments before the jeep exploded.
The epilogue shows Senapathy calling Krishnaswamy from Hong Kong indicating that he will be back when the need for him would arise.