Ochayi Revathi, a widow, lives in Karisalpatti village with her son Veerannan Nizhalgal Ravi, a school dropout. Ochayi's daughter is married to Mookkaiya Thevar, whose daughter is Muthupechi. Malaichamy Thevar, the chief of the neighbouring village, is the patron of the village school where children from both settlements study. Mookkaiya Thevar leads a double life, maintaining an extramarital affair with Hamsavalli and spending much of his time and money on her. Though Muthupechi secretly nurtures a desire to marry her maternal uncle Veerannan, she hesitates, since their families are not on speaking terms due to an old dispute over a field that was meant to be gifted as dowry at the time of his wedding. Mookkaiya, despite having a grown daughter, pressures Ochayi to secure the dowry owed to him, but Ochayi refuses, wary that the money would simply fund his other affairs.
A new teacher arrives in the village and quietly falls in love with Muthupechi. When Muthupechi reaches puberty, Mookkaiya organizes a ceremony but deliberately excludes Ochayi and Veerannan from performing the rites. Enraged, Veerannan causes a disturbance, and the villagers side with him, urging Mookkaiya to include Ochayi and Veerannan. Reluctantly, Mookkaiya relents, and the rituals proceed. Muthupechi feels a swell of happiness at finally being noticed by Veerannan, who had previously ignored her. The young man, now drawn to her, begins meeting her in secret and promises to marry her. In the meantime, Hamsavalli's brother Muthukalai questions why Mookkaiya was left out of the ceremony. Although Mookkaiya is entangled with Hamsavalli, he looks down on her brother’s desires and resents the intrusion.
At the jallikattu festival, Veerannan fights Malaichamy’s bull and wins a gold chain as a prize. Enraged by the victory, Malaichamy schemes to teach Mookkaiya a lesson by using a bet that would decide who wins Muthupechi. He manipulates the situation so that the person who controls Mookkaiya’s bull could win Muthupechi. Muthukalai laces Mookkaiya’s bull with herbs to influence the outcome, allowing Malaichamy’s man to subdue it. Malaichamy then demands that Mookkaiya arrange a marriage between Muthupechi and the winning man. When Mookkaiya returns home, his wife rebukes him for treating his daughter as a prize. Realizing his mistake and the precarious political balance he’s disturbed, Mookkaiya kills his own bull and then himself.
Malaichamy does not give up; he appeals to the Karisalpatti Panchayat and demands that Muthupechi be married to his chosen man. The Panchayat refuses and suggests Malaichamy forget the bet. He challenges them again, and the Panchayat makes arrangements to marry Muthupechi to Veerannan by the next morning, hoping to end the matter. On Veerannan’s way back with the required items, Malaichamy’s hoodlums ambush him. He fights and defeats several of them, but fearing arrest, he escapes and is presumed dead by villagers. Malaichamy, undeterred, camps at Karisalpatti and presses for Muthupechi’s hand. When the Panchayat again refuses, a clash erupts between the two villages. The police intervene, ban the Panchayat, and restrict movement. Enraged, Malaichamy shuts down the village school, which the teachers manage to reopen by teaching outdoors.
To pressure the Karisalpatti people, Malaichamy orders women from Karisalpatti to return to their homes, prompting many to leave. Muthupechi sinks deeper into guilt and worry for Veerannan, who has not contacted his mother since vanishing. The village school teacher, who loves Muthupechi, begins sending her letters in Veerannan’s name, bringing some comfort and hope to her family. A year passes with the stalemate ongoing. Then two letters arrive: one from Veerannan announcing his return, and another from the teacher. Muthupechi is thrilled and waits eagerly for Veerannan’s arrival. The next day, Veerannan returns, accompanied by his wife, leaving both Ochayi and Muthupechi stunned and speechless. Veerannan explains the circumstances that forced him to leave—the army, then marriage—to safeguard her future. Muthupechi can empathize with the villagers’ plight and their sense of duty. Malaichamy returns with his followers and reiterates his demand for Muthupechi.
The villagers of Karisalpatti decide they’ve had enough and propose that Veerannan take Muthupechi as a second wife to protect the village’s honor, but Muthupechi declines, mindful of Veerannan’s wife. The villagers grow angry and, feeling betrayed, excommunicate Veerannan and Muthupechi. Malaichamy, sensing weakness, ultimately abducts Muthupechi. Veerannan learns of the kidnapping and rushes to confront Malaichamy’s forces, determined to rescue her. In the ensuing fight, Veerannan’s wife is killed by Malaichamy. Enraged, Muthupechi seizes the temple’s trident to kill Malaichamy, while Veerannan, after overpowering the remaining attackers, also strikes down Malaichamy. In the end, Muthupechi realizes the depth of Veerannan’s love as she dies by his side.
