After 15 years in prison, Pazhani secures a job as a driver for Jeevanandham. He soon discovers Jeevanandham's wife, Karpagambal, is his estranged sister. Hiding his identity, Pazhani adopts the name Vellaiyan, knowing she has hated him since childhood. While Pazhani falls in love with Deepti, he learns Jeevanandham has a greedy concubine named Durga.
When Karpagambal discovers Pazhani's identity, she furiously fires him. A flashback reveals Pazhani was jailed at age 10 for murdering his father's concubine to protect his mother. Learning the truth, Karpagambal forgives him but asks him to stay away. However, Jeevanandham schemes to divorce Karpagambal, conspiring with a moneylender, Vaikundan, to steal her home. Pazhani intervenes, tricking Jeevanandham into transferring his export firm to Karpagambal, leaving him penniless. Durga subsequently abandons Jeevanandham for Vaikundan. Pazhani kills both Durga and Vaikundan to protect his sister. Returning to jail, Pazhani feels content, having sacrificed his freedom for both his mother and sister.