The story begins with a young couple, Balu and Ishwarya, being chased by some goons. Ishwarya is the daughter of Rajadorai (Charan Raj) and had eloped and run away with Balu against the wishes of Rajadorai. Rajadorai sends his goons to track down the couple. When the goons finally track down the couple in a forest and start beating up Balu, a man (Rajinikanth) comes to the couple's rescue. When Rajadorai and his brother Ramadorai (Nizhalgal Ravi) find out about this man, they rush over to the man's hideout in the forest, only to escape in fear when they see him. The couple is scared and puzzled as to how such a man could induce so much fear in the brothers. The man's wife Parvathi (Gouthami) then tells the couple the story of the man, whose name is Dharmadorai.
Dharmadorai was a farmer in a village named Valliyur. He was the elder brother of Rajadorai and Ramadorai. He had showered so much love and affection on his younger brothers and even borrowed money for their "education", much against his father's (Madhu) wishes, who was convinced of the scheming and evil nature of his younger sons. He even got Rajadorai married to Vaibhavi (Vaishnavi), a girl whom Rajadorai had raped, to save him from a jail term. The brothers however, showed no sort of affection to Dharmadorai and used his innocence for their sinister desires. They convinced Dharmadorai to borrow 6 lakhs so that they could start a "business". Using this money, Rajadorai and Ramadorai moved to Madras (now Chennai) and went into smuggling. They later double-crossed their smuggler boss Jose by lodging a police complaint against his son Ajay (Ajay Rathnam) for their own benefit and soon became rich due to their illegal activities.
One day, Dharmadorai went to Madras when he heard that Ramadorai was going to get engaged to a rich girl and leave for America. The brothers did not receive him warmly and humiliated him that evening at a farewell party organised for Ramadorai. Later that night, Ajay, who had been released from jail, entered their house to kill Ramadorai in retaliation for having double-crossed Jose. Ramadorai eventually killed Ajay and convinced Dharmadorai to take the blame for the murder. Dharmadorai was sentenced to 7 years imprisonment as a result. The brothers then got Jose and his henchmen also arrested. While Dharmadorai was in jail, Parvathi gave birth to a baby boy.
A few years later, Rajadorai and Ramadorai decided to sell off their father's house and property to repay the 6 lakhs. When their father opposed this, the brothers killed him and drove Parvathi and her son out of the house. With nowhere else to go, Parvathi and her son moved to Madras. The small boy too got killed by Ramadorai when the boy recognised him as the murderer of his grandfather. With no home, her husband imprisoned and her son dead, a grieving Parvathi took up the job of a housemaid in Madras.
Soon, Dharmadorai completed his jail sentence. When he found out about Parvathi's plight and how his brothers had betrayed him, he rushed over to the brothers' house and mercilessly beat them. Following this, he disowned them and moved to the forest with Parvathi.
In the present day, Jose and his henchmen get released from jail and kidnap Rajadorai and Ramadorai in retaliation for putting them in jail. On Parvathi's advice, a reluctant Dharmadorai goes to rescue the brothers. He rescues the brothers and finally forgives them.