Ganesh, a young man with a deep fear of ghosts who refuses go out after 6PM, moves into a new house with his mother, father, and wife Priya. All of a sudden, Ganesh is possessed by a ghost and starts behaving in a rude manner; his family cannot understand his behaviour, so they seek the help of a priest named Andaiyar. Andaiyar asks the ghost about his past. The ghost says that he is Muniyaandi and starts revealing his flashback.

Muni was a kindhearted but poor man living in the slums with his daughter. His friend is MLA Marakka Dhandapani, who uses Muni to win local elections and promises that he would give lands to the poor villagers. Dhandapani wins the election but cheats Muni. Muni fights with Dhandapani, who kills Muni and his daughter. Dhandapani lies to the poor people by saying that Muni and his daughter fled with the money that he had given Muni for the welfare of the villagers.

Ganesh enters Dhandapani's household and terrorizes him and his assistants. Dhandapani learns that Muni's spirit is in Ganesh's body, so he gets a shaman named Mastan Bhai to save his life. Bhai bargains with Muni, who agrees to let Dhandapani go if he repents and helps the poor villagers. In the climax, at Ayyanaar temple, Dhandapani confesses to the people that he killed Muni and his daughter. He then leaves money with the villagers. Muni talks with the people and eats the feast prepared by them. Bhai tells Muni to leave Ganesh's body, and he does. However, Dhandapani lied and was planning to get back all his money from the villagers. Ganesh, upon hearing this, kills Dhandapani. Bhai sees this act but does nothing, as he finally sees the injustice done by Dhandapani.