Ganesh, a man with a deep-seated fear of the dark and every nightfall, refuses to step outside after 6 PM and relocates to a new house with his mother Ganesh's mother, his father Ganesh's Father, and his wife Priya. Soon after settling in, Ganesh is overtaken by a ghost who begins to act in his stead, surprising his family with sudden rudeness and confusing behavior. Desperate for help, they turn to a priest named Andaiyar, who presses the spirit to reveal its own history. The ghost identifies itself as Muniyandi and unfolds a tale from the past that casts a long shadow over the present.
Muni was once a kindhearted, impoverished man living in the city’s slums, where he shared a fragile bond with his daughter. His trusted ally is MLA Dhandapani, a politician who exploits Muni’s credibility to win votes and promises the poor lands and prosperity in return. Dhandapani wins the election but betrays Muni, leaving him to fight against the very schemes he helped empower. A brutal confrontation ends with Dhandapani killing Muni and his daughter, and he then deceives the villagers by claiming that Muni and his daughter disappeared with the welfare funds meant for them.
Moved by the sorrow and injustice of Muni’s past, Ganesh resolves to help, even going so far as to ask Andaiyar to lie to his own family by saying the ghost has departed, a request Andaiyar grants. Possession returns, and Ganesh, now embodying Muni, secures a job as a bodyguard for Dhandapani’s daughter. The plan hits a dangerous snag when Ganesh – still Muni in spirit – brutally kills Dhandapani’s brother, prompting the jealous and vengeful politician to uncover Ganesh’s true identity and hire an exorcist, Mastaan Bhai, to free himself from the haunting threat.
Bhai captures Muni and bargains with him: he will permit Dhandapani to go if he repents and lends a hand to the villagers who were left poorer by his schemes. The ensuing climax unfolds at the Ayyanaar temple, where Dhandapani finally confesses publicly that he killed Muni and his daughter, and he leaves money with the grateful villagers. Muni speaks with the villagers and shares a feast prepared for them, while Bhai instructs Muni to depart Ganesh’s body, which he does. Yet the truth behind Dhandapani’s charity remains murky, as he had intended to reclaim his ill-gotten wealth from the people. In a final, stark twist, Ganesh kills Dhandapani after learning of his deceit, a moment Bhai observes with silent resignation, recognizing the broader injustice that fueled the tragedy.
