Mangalam, the only daughter of village elder Ponnambalam, grows up sheltered in a close-knit community as she prepares for the visit of her prospective groom. The groom, Chella Durai K. Bhagyaraj and his family arrive at Mangalam’s home, and Chella Durai quickly feels a pull toward Mangalam Sulakshana, a shy and innocent girl who moves with quiet dignity. The next day, a riverside encounter unsettles her, and she panics, while her uncle, the martial arts trainer Nambiar M. N. Nambiar, misreads the moment as a misstep by Chella Durai. He orders his men to confront him, a confrontation that Chella Durai easily wins, forcing Nambiar to acknowledge that Chella Durai is indeed Mangalam’s intended match.
Meanwhile, Ponnambalam’s brother-in-law Ayyavu harbors an unspoken love for Mangalam and remains out of the loop about the groom’s arrival. The families seek an astrologically favorable wedding date, but none exists for that month, so the plan is to push the ceremony to the following month. The dynamic becomes tenser when Chella Durai himself visits Mangalam’s house and finds her alone and fearful; she runs away, and Nambiar steps in with a scheme to boost the courtship. Chella Durai accepts the plan and, in a bold move, abducts Mangalam, a turn that gradually unlocks her reserved heart.
On the night of a new moon, Nambiar conducts rites for an unnamed person who died by suicide, while Chella Durai continues to try to demystify matters of sex for the increasingly receptive Mangalam, who cannot fully articulate her feelings yet. The more time they spend together, the deeper her affection grows for him. But the path to marriage is blocked by financial strain: Chella Durai’s stepmother demands a larger dowry than Ponnambalam can provide, and Chella Durai’s attempt to shield Mangalam by gifting money to his own father humiliates Ponnambalam and ends with his outright refusal.
Mangalam, mindful of her father’s honor, urges Chella Durai to seek another match, yet the bond between them persists. Chella Durai’s impulsive zeal leads him to consider eloping, but Mangalam remains steadfast in her sense of duty to her father and to her own dignity. When Chella Durai’s family discovers him trying to steal money to run away, they lock him in a room. Mangalam waits for sunrise, returning home alone as Chella Durai fails to show. Back at home, Ponnambalam nearly takes his own life, and Nambiar intervenes to save him. This crisis plants seeds of doubt in Ponnambalam about Mangalam’s innocence, and Mangalam’s painful act of burning her feet after overhearing his harsh suspicions underscores the emotional stakes. Eventually, Ponnambalam learns the truth and forgives Mangalam, though his distrust of Chella Durai remains.
Nambiar then invites Chella Durai to stay with him and presses to sway Ponnambalam, while Mangalam reiterates that she will marry only with her father’s blessing. The uncle issues a challenge: unite Mangalam and Chella Durai within one month or lose half his moustache, a vow that triggers a charged panchayat and leaves the village choosing sides. With only 15 days left, Chella Durai takes the wedding thread to Mangalam and engages in a brave, lone fight against Ayyavu and his men. In the final phase of the challenge, Nambiar mobilizes a wave of pressure, urging men in buses to visit Mangalam and reject her suitor to test her resolve. Ponnambalam lashes out as seven prospective grooms reject Mangalam, deepening the family’s crisis.
Facing mounting cruelty and the threat to Mangalam’s future, Chella Durai contemplates leaving the village. Yet Nambiar refuses to let him go, fearing the ego clash that would erupt once the challenge ends. The two men collide in a decisive confrontation, and Chella Durai emerges victorious over Nambiar, though the victory is tempered by the weight of their shared history and the bonds they have formed.
Nambiar then leads Chella Durai to a grave where rites are performed and reveals a painful truth: the tomb belongs to his own former lover from four decades prior, a woman who died after he abandoned her. This revelation explains why Nambiar fears Mangalam’s potential heartbreak and why he pushes Chella Durai to marry her at all costs. With renewed determination, Nambiar persuades Chella Durai to press forward with the marriage.
The next day, Ponnambalam makes a drastic decision to arrange Mangalam’s marriage to Ayyavu and issues invitations throughout the village. Mangalam’s mother and grandmother, however, urge her to elope with Chella Durai to resist her father’s arrogance and protect Mangalam’s happiness. Ponnambalam overhears this and recognizes his earlier misjudgments; he forgives Mangalam and tears up the invitations, a move that further infuriates Ayyavu. In a final, brutal twist, Ayyavu stabs Ponnambalam, and Chella Durai acts to subdue him. Ponnambalam bleeds out, and in his dying moments, he signals his consent to Mangalam’s marriage to Chella Durai, sealing their fate together.
