Job candidates Raghunathan and Suguna appear for an interview. When Suguna learns that Raghu is more qualified than her and has better chances of getting selected, she poses as the manager of the organisation and tells Raghu that the vacancy is already filled, and he would be considered for a vacancy that is likely to arise after a week. Raghu believes her and leaves, and Suguna gets selected. Soon Raghu lands at Suguna's house with goods and gifts for her family members and pressurises Suguna to recommend his name for the vacancy he had discussed with him. Suguna gets worried and tries to avoid Raghu. Coincidentally, a vacancy arises and when an advertisement is released, Raghu attends the interview. Impressed with Raghu's qualifications and talents, the owner appoints him as the Assistant Manager. On joining duty, Raghu learns of Suguna's manipulation. Though initially angered, he gets attracted to her intelligence and falls in love with her. She too falls in love with him and they marry.

After marriage, Suguna quits her job and becomes a housewife. She becomes possessive of Raghu and slightly insecure about his fidelity, declaring to commit suicide if he indulges in adultery. Raghu leads a righteous life with her. He gets introduced to Suguna's friend Jaya, a widow, who seeks the couple's help to sort out an issue relating to her deceased husband's insurance claim. At Suguna's request, Raghu helps Jaya. Later when Raghu is going to Jaya's house, his clothes become soiled and he goes to a bathroom of Jaya's house to wash. Jaya and Raghu end up having sex, but later regret it. Unable to cope with suppressing this fact from Suguna, Raghu comes home drunk. Raghu's behaviour makes Suguna suspicious and she discovers the truth. Devastated, she returns to her original house. Suguna's father says that her life should be with her husband, otherwise she should live on her own. Suguna files for and receives divorce, later realising she is pregnant. She delivers a boy named Suresh and struggles with him.

Five years later, when Suguna and Suresh travel to Madras via bus, they meet Raghu. After reaching Madras, Suguna sees that Raghu is the new manager in her office. She tries to resign, but ultimately does not. Raghu tries to justify his predicament but Suguna continues to avoid him. He leases the house opposite Suguna's and tries to befriend Suresh, much to Suguna's annoyance. Suresh realises that Raghu is his father and bonds with him. Meanwhile, Suguna berates a colleague for inappropriate behaviour and he apologises, slowly comes closer to Suguna and she trusts him. When Suguna learns that Raghu leaves office everyday to be with their son, she tries to threaten him. Raghu gives her 30 days to return to him, threatening to take a strong decision if she fails. During these 30 days, various incidents taking place in Suguna's life change her perception about men, specifically Raghu. Suguna learns that Raghu had been financially supporting her father.

Later, the colleague whom Suguna trusted boasts to the other employees about having an affair with Suguna. To "prove" it, he enacts a drama. He asks her to come to a lodge to take her son, who is believed to have been kidnapped, but locks her in the room. 15 minutes later, he goes out and pretends to have had sex with her. As a result, the entire office speaks ill of Suguna. She is devastated, but becomes pleasantly surprised when she overhears Raghu's comment on her character. Raghu says she is like fire as she would never allow anyone to touch her; if anyone did, she would burn them and herself. Raghu beats the colleague and forces him to openly confess. Suguna regrets misunderstanding Raghu and not forgiving him. She decides to return to Raghu, only to realise the 30-day deadline has ended, and he is remarrying. Suguna fails to stop the marriage and decides to commit suicide along with Suresh; he refuses and requests to live with his father. Before Suguna can commit suicide, however, she learns that the "remarriage" was merely an act. The family reunites.