Rajasekharan alias Raju becomes the guardian to his younger sister Radha after their parents' death. When the factory where Raju works is closed due to a labour problem and he is depressed, Radha gives him ₹1000 which she had earned and saved by making toys. She advises him to use this money as seed capital and commence his own toy business. Raju assents, and in a short time, becomes rich. Anand, a former colleague of Raju, is jobless and approaches Raju for work. Raju appoints him in his concern and over a period of time, Anand and Radha fall in love. Raju, who is very possessive of his sister, gets angry with Anand as he feels betrayed. However, knowing how intensely Radha loves Anand, he arranges their wedding.

After the marriage, Anand, along with his aunt and cousin, move into Raju's house. Raju marries Malathy, a doctor, on Radha's suggestion. All of them continue to live under the same roof and several misunderstandings arise. Anand's aunt uses every opportunity to widen the rift between Malathy and Radha and Radha and Anand. Unable to witness Radha's troubles, Raju moves out of the house with his wife. Through Radha, Anand's aunt serves a legal notice to Raju, demanding a share in the property for Radha. Malathy files a counter petition and the property is attached by the court, pending resolution. Unable to see Radha's sufferings, Raju withdraws the case. Still the families do not unite.

Radha delivers a girl and Malathy delivers a boy. After her child's birth, Malathy goes abroad for further studies, leaving the child with Raju. Unable to cope with the separation from his sister and to have peace of mind, Raju goes on a pilgrimage for several months. He returns on Diwali day and goes to meet Radha, but is denied entry by Anand's aunt. While going back, he saves a little girl from getting burnt by firecrackers and in the process, loses his eyesight. He is hospitalised and Radha rushes to the hospital to see her brother. Raju learns that the girl he saved is none other than his niece. Unable to cope with his inability to see them, he dies; Radha too dies holding his hand. Anand comes after and feels bad for Raju and Radha, and on their behalf, Anand takes care of Radha's daughter and Raju's son.