The movie starts on a stormy night in Kerala. A large tree branch falls and breaks the roof of an outhouse, releasing a dark entity. The woman inspecting the outhouse ends up in a hospital suffering from a coma.
In another town, the woman’s daughter, Sanjana (Bipasha Basu), and her husband, Kabir (Karan Singh Grover), argue about not being able to celebrate her birthday together. Sanjana gets a call about her mother’s accident and they quickly fly to Kerala. In Kerala, Sanjana begins having visions that make her believe her dead conjoined twin’s soul is after her. Her husband does not believe her, and sends her to his former professor for spiritual healing.
During the treatment period, she tells the professor about how her conjoined twin sister Anjana (Bipasha Basu) always hated that Kabir liked Sanjana more than her. In fact, it was when Kabir told Sanjana that he was coming back home from abroad that Sanjana decided to separate from Anjana. It was during this operation that Anjana died, and Sanjana blames herself for her sister’s death. The professor reassures Sanjana that her visions of Anjana is the result of her guilt and only a figment of her subconscious.
At her mother’s place that night, Sanjana is forced into the outhouse by an unseen entity. Hearing noises, Kabir wakes up and finds her unconscious in the outhouse. When Sanjana awakes, she is possessed by Anjana’s soul. After this, Sanjana/Anjana can’t get enough of Kabir. When the professor meets her again, he feels there is something wrong and tells Kabir to keep an eye on her, which she overhears.
The caretaker suggests that a ritual be performed on Sanjana/Anajana. After the ritual, Anjana’s stronghold on Sanjana escalates and her true colors are shown, resulting in an exorcist being called in.
During the exorcism, Anjana reveals that she was murdered. As she leaves Sanjana’s body, she urges Kabir to discover the truth of her death. After Sanjana wakes up, Kabir threatens to leave her. Sanjana tells him that years ago when he called her to tell Anjana that he was coming home, Anjana lost her mind and tried to kill her because she had feelings for Kabir too. In self-defense, Sanjana hit Anjana on the head with a glass music box, killing her. Their mother covered the truth to protect her daughter. After consulting with the professor, they try to find and burn the last possession of Anjana and set her soul free.