Vasanth (Aari Arujunan) is an artist who is working on a story about 'Mayavanam', a haunted forest. On his friend's birthday, he tells a story involving 'Maya', a malevolent spirit. He tells him about how one experiences chills and witnesses a spirit descending on them when one says "Maya! Your daughter is not with me!" three times. To mock Vasanth, the friend says the same three times, and a similar figure enters the room. He falls back in fear, but the figure reveals itself as his wife; it's just a birthday surprise. The next day, Vasanth shows the pictures taken by him during the dressed up Maya's entry to his boss, Ram Prasad (Amzath Khan) and Madan (Uday Mahesh), the episode writer on Mayavanam. Ram points out a smoky form near them and warns him of it. He tells him about a book, Asylum by Kate, that details the life of the mentally ill who were forced into asylums and experimented upon. Madhan then recounts the story of one such inmate, a woman named Maya Matthews, who was taken to the asylum after murdering her husband and forced to give up her newborn daughter to the authorities in the asylum. She falls to her death from the building, with an expensive ring rumoured to be on her body, and is buried in the grounds of the asylum (Mayavanam), where it is believed her vengeful spirit now roams. Later, Madhan and Vasanth's friend—an auto driver—visits Mayavanam to write about his last episode. Madhan disappears, and after escaping from Mayavanam somehow, Vasanth's friend meets with a grisly death soon, by falling off the building just like Maya, which spurs Vasanth to embark on an investigation into Mayavanam.

In alternating scenes, Apsara (Nayanthara) is a single mother struggling to make ends meet by working in ad films. She is separated from her husband Arjun who is an actor and lives with her friend Swathi (Lakshmi Priyaa Chandramouli) who works at a film production house, RK Studios. After a poster of the film, Irul, that Swathi is currently working on is put on the walls of the house, Apsara experiences strange things happening inside the house. She doesn't give much thought to it because she is always preoccupied with the loan that she has taken from a local gangster. He keeps visiting her house demanding cash and she keeps putting it off by saying that the cheque she has been entitled to, after acting in another ad film previously, keeps bouncing off. In frustration, she goes to visit the ad company where she learns that the producer has gone to take part in the contest arranged by Swathi's company. The contest is a promotional ad for Irul, in which contestants are awarded ₹5 lakh if they succeed in watching the horror film alone at night without showing signs of fright. She catches an auto and goes to the studio. The scenes are alternated with Vasanth going to Mayavanam and the ad film producer watching the film. By the time she reaches the studio, the producer is dead and is taken on a stretcher towards the ambulance. The director of Irul had witnessed the bizarre death of the ad film producer while watching the film but claimed to the police it was a heart attack.

All lost and her being emotionally tortured by the moneylender, Apsara decides to watch Irul, to make ends meet. Swathi begs her not to, fearing for Apsara's life and in hope of the director backing her up, she appeals to him too, but the director supports Apsara even though he knows what could happen later on. The film starts to play, and it is revealed that Vasanth's side of the story is the film Irul. As Apsara continues to watch, she is inexplicably teleported into the film. Ram and Kate, the author, is shown to make a man dig into the grounds of Mayavanam, searching for the expensive ring that Maya was said that died with. Vasanth gets caught by Kate and is held at gunpoint while they search for the ring. Apsara gets caught too, and when they eventually find Maya's coffin, a figure is seen to appear behind Kate and Ram, and all hell breaks loose. Soon Apsara and Vasanth get separated from the group and are chased by the ghost. They fall into a big ditch and Vasanth helps her out, while he stays in. She runs away and hears a baby's cry. She goes in search of it when she gets shot by Shankar. After falling, she is held by Maya who cries out in bitter rage and kills Shankar. It is then revealed that Maya is Apsara's mother. She wakes up in the theatre, with her mother's diary on her lap, and the doll, which Maya had brought for her baby. It is later revealed that the person who played Vasanth in the film is Arjun himself and the producer of the ad film who died earlier, was the one who sent Maya to the asylum and took her ring.

The final scene shows Apsara reunited with her husband and now acting in a film about Maya directed by the same director as Irul. As the shooting starts, the first scene being Maya sitting in a wheelchair, Arjun finds Apsara standing in a corner while everyone was assuming that she was the one sitting in the wheelchair. The film ends with the spirit of Maya killing the director and Maya's ring falling out of his pocket. After that Maya turns back and the screen cuts black.