Selvam and his friend Bhaskar are petty thieves, who live their lives by stealing stuff from people. One day, they are assigned a job to steal a Ganesh Idol from the temple, for a man who had just moved into a new house, citing prosperity as a reason. The friends succeed in stealing the idol but are spotted by the people who start chasing them. They hide in a house and encounter Radha. Radha is a maid in the house and is looking after the owners' three children while the adults are away on pilgrimage tour. Radha and the kids lock the two of them in a room and order them to do stuff for three days. Radha, while spending time alone in the house with the guys, realise that they are not bad after all and develops a soft corner for Selvam and he in return, falls for her. The guys are released after three days, the day the owners are to return. Bhaskar steals Radha's handbag which contains her diary. Selvam reads the diary and finds out that Radha is the illegitimate daughter of Vishwanathan. After her mother's death, Radha meets her father who accepts her as his daughter but has to bring her into the house as a maid. Vishwanathan's second wife and her sister take an instant dislike for Radha. They treat her with utter disgust and blame her for the tiniest of the things. Vishwanathan plans to arrange the marriage between Sanjay, his brother-in-law and Radha. But Sanjay says that he would have to think about it and asks for three months time. Radha waits for his reply. Selvam, after reading her diary, feels pity on her and tries to change his ways by working responsibly after Radha's advice. He also hides his feelings for her.

After returning from the trip, Vishwanathan's wife finds out that her diamond necklace is missing. When looking for it, she finds a cigarette bud in one of the drawers and scolds Radha. She chases her out. Selvam who comes to return her bag, finds out and helps her to accommodate in a hostel. He does many petty works to pay the hostel fees and help Radha. One day, Selvam finds about Radha's singing talent and tries to help her move on with it. He encounters music director Gangai Amaran late one night and helps him repair his car. In return, he asks the director to help Radha out. Radha, after singing a few songs, becomes successful in her singing career and becomes rich. She stays in her bungalow with Selvam and Bhaskar. During an interview, Radha refrains from saying her father's name. Upset, Vishwanathan reveals that he is the father. His wife, looking at Radha's money, accepts Radha as her daughter as well. They come to stay at her house. Vishwanathan's wife does not like Selvam and Bhaskar staying with them. They plan the wedding of Sanjay and Radha, as Sanjay had accepted to marry Radha, long time back. When Radha had gone out of town with Sanjay, to receive an award, Vishwanathan's wife and sister-in-law stage a drama that Selvam stole Radha's money and chase him and Bhaskar out. Radha comes back and is shocked. She finds Selvam's diary in his room and understands his love for her.

During an award ceremony, Radha reveals that the reason for her success is not her family but Selvam and she had fallen in love with him. She also tells her desire to marry him. Selvam who had arrived there to drop a passenger, sees it and is called upon the stage when Radha sees him in a TV. In a flashback, it is shown that Radha had informed Sanjay and Vishwanathan about her love for Selvam and how Sanjay had accepted it. Selvam and Radha leave the place hand in hand.