Thenmozhi is a textile factory worker in a village. She develops a liking for Ulaganathan, an idealist in the same village who is respected for his integrity and selflessness. Upon the approval of Ulaganathan's father Brahmanayagam, Ulaganathan and Thenmozhi marry on 15 August, India's Independence Day. The couple lead a happy life and work for the welfare of the village.

Members from the Yellow political party want Ulaganathan to join them. At first he declines, but they lure him by promising to provide him with a ministerial position if the party wins. Thenmozhi becomes upset with the developments as she notices a significant change in Ulaganathan's attitude. She argues with him frequently about this, but he is unfazed. When Thenmozhi becomes pregnant, she goes to her visually impaired father's home for delivering the child.

By the time Thenmozhi returns with their child, a son, Ulaganathan has left the Yellow party to join the opposing Purple party, the result of party switching. He also shifts to a new house gifted by the Purple party. Thenmozhi, who is unable to accept his lack of loyalty, futilely argues with him. He orders her to remain completely obedient to him without arguing or advising. The rift between them becomes wider when Thenmozhi refuses to satisfy Ulaganathan's sexual desires, citing his lack of loyalty.

Alangaram, who previously wanted to marry Ulaganathan, becomes his mistress and Ulaganathan neglects Thenmozhi. Alangaram and her mother slowly take control over the household, with Brahmanayagam powerless. Thenmozhi's brother Suthanthiram, who had run away in childhood, returns and fights for his sister's rights, but fails as he is silenced by Ulaganathan with money. All of this causes Thenmozhi to leave with her child to her father's home. Once when she is not home, the child which was left in her father's custody, takes infant steps, and is washed away in a flood. Ulaganathan arranges for his father-in-law's eye surgery, and Thenmozhi becomes isolated with everyone supporting Ulaganathan.

With Ulaganathan's party having become weaker, he is advised by the party chief to assemble more members to make the party stronger. Ulaganathan plans to organise a communal riot in the village to lure people to his side. Alangaram overhears this, tells Thenmozhi, but drowns in quicksand when escaping Ulaganathan's henchmen. Thenmozhi asks Ulaganathan to end his atrocities and surrender. But he mocks her and advises her to join him for the upcoming Independence Day ceremony, which is also their wedding anniversary.

The next day, Thenmozhi comes to the ceremony, where a statue of Mahatma Gandhi is to be unveiled by Ulaganathan, with a large garland of flowers and garlands him. As Ulaganathan expresses happiness about his wife's apparent return to his side, she takes a knife hidden in the garland and stabs him to death. The police arrest Thenmozhi and Suthanthiram sombrely sits under Gandhi's statue.