In 1948, Kadhiresan visits a magnificent palace built by King Veera Sethupathi and wishes to own such a palace himself. In 1966, Kadhiresan's niece is possessed while cooking in the palace for her husband and daughter. Afterward, the family dies in their sleep and reunites with other family members who died in the palace. With them is Kadhiresan's dead cook, Shanmugam, who claims that a mysterious force compels him to poison the inhabitants of the palace every full moon and that a person who survives the poisoning will set them free. Until then, the spirits, including Kadhiresan (who has become a recluse), are trapped in the palace.In 2021, Rudra's family are thieves, feuding with two other thieves. The dispute lands them in front of police Inspector Kadhir, the great-great-grandson of Kadhiresan. Kadhir and his grandfather, Vikram, wish to sell the palace but are stymied by rumors of the palace's haunting. Kadhir hires Rudra's family to supposedly clean the palace. In reality, he wants them to live there until the full moon to prove that the palace is safe. Rudra's family agrees to clean the property, planning to loot the palace.When Rudra first steps foot in the palace, the ghosts feel mysterious energy and hope that she can set them free. Rudra, who has been enchanted by the palace, plots with her family to fake a haunting so that they can acquire the palace cheaply. Kadhiresan's ghost, spooked after seeing Rudra, begins to secretly follow her around. On the day of the full moon, Rudra's family goes to the temple, leaving Rudra behind. Shanmugam possesses Rudra's mother to cook for her. Rudra eats and falls asleep. Though she survives, when she wakes up, she can see the ghosts. After hearing their story, Rudra promises to free them, in return for them helping with her plan.Shanmugam later takes Rudra to a secret room in the palace, which holds pictures from the 1940s of a woman resembling her. Shanmugam tells Rudra the story of Veera Sethupathi, who built the palace for his beloved queen, Annabelle. The two live happily, but Kadhiresan begins to covet their home. After Veera Sethupathi refuses to sell the palace, Kadhiresan poisons the couple. A pregnant Annabelle dies after swearing vengeance. This is secretly seen by the couple's cook, Shanmugam. After Kadhiresan and his extended family move into the palace, Shanmugam poisons their food. Kadhiresan suspects Shanmugam and forces him to eat first, which Shanmugam does without hesitation. By the next morning, Shanmugam, Kadhiresan, and his family are all dead, except for Kadhiresan's grandson, Vikram, who had missed the meal. Since then, Shanmugam has been killing Kadhiresan's relatives who move into the palace. The sole survivors of the family are Vikram and Kadhir.When Kadhir attempts to kick Rudra's family out of the palace, a mysterious force throws Kadhir and his goons out, surprising the ghosts who hadn't been able to interfere. Shanmugam fails to convince Rudra that she is the reincarnation of Annabelle. The ghosts overhear their conversation and are angry at Shanmugam's deceit. Kadhir and his goons return with Vikram, who believes that Rudra is Annabelle. He decides to kill her to satisfy his grandfather's ghost. The ghosts of Kadhiresan's family acknowledge Rudra as the rightful owner of the palace and combine their powers to stop Vikram from hurting her. When a new arrival enters the palace, they once again feel the energy that accompanied Rudra's arrival, and finally, at peace, disappear.The new arrival, a government official resembling Veera Sethupathi, tells the assembled parties that the government will seize the palace as a heritage-listed tourism site. Rudra and her family depart in a huff. The government official, having fallen in love with Rudra at first sight, proposes to her. Rudra accepts with a smile. Shanmugam, watching their reunion, is finally at peace and disappears. Alone in the palace, Kadhiresan's ghost attempts to leave but is shocked to find that he is still trapped. The movie then returns to the scene where Kadhir and his goons were pushed out of the palace, hinting at a sequel to the story.