Arjun Bhagwat (Emraan Hashmi) is an ex-police officer who is hungry for money and earns his bread by doing wrong things. He is an atheist (Nastik) but regularly visits church to donate money to orphans. Priya (Jacqueline Fernandez), a model, is in a passionate but confused relationship with Arjun. Whilst Priya is in love with Arjun, Arjun merely lusts for her.He captures her and makes love with her.
Arjun meets a gangster, Sameer, who has been going through a slump in his business due to an unexplained disappearance of his hookers. Sameer offers him a huge amount of money to locate the missing girls, which Arjun accepts. During his investigation, Arjun finds a phone number linked to the missing girls. He tells Sameer to send a prostitute to the number. Sameer decides to send Reshma (Sulagna Panigrahi), a 17-year-old college newcomer in the business, who has entered prostitution to feed her family, though keeps this a secret from them. Reshma is sent to the house of Dheeraj Pandey (Prashant Narayanan), who is actually a psychopath murderer responsible for torturing and killing the missing hookers. He decides to do the same with Reshma and throws her in a dark well, with the intention of torturing her till her death.
Arjun finds out that Dheeraj is the murderer and tells the police. While Dheeraj is held in jail, the commissioner calls a psychiatrist to extract his confession. Dheeraj tells the doctor that he kills women because he thinks they take advantage of men. He also reveals that he castrated himself and became an eunuch to get rid of his sex addiction, with the help of a fellow eunuch and big-shot politician, Nirmala Pandit. Dheeraj is eventually let out under Nirmala Pandit's influence. Meanwhile, Reshma escapes from the well and tries to find her way out through the forest.
Arjun meets Dheeraj's family, who reveal that Dheeraj used to beat his wife. He next meets a private dancer, Sonia, who had also been tortured by Dheeraj, but managed to escape. Arjun then meets an idol-maker who used to work with Dheeraj. The maker tells him that Dheeraj used to make idols of devils instead of deities and killed the factory-owner who tried to stop him. Inspector Siddharth (Sudhanshu Pandey) informs Arjun that Dheeraj is free, and the police try to track him down as quickly as possible. Nirmala and Dheeraj enter the same temple where Reshma is hiding. Nirmala and the priest, who had both been unaware of Dheeraj's true nature, are killed by Dheeraj, but not before the priest reveals that Reshma is there. Dheeraj finds the terrified Reshma and brutally murders her, escaping just before Arjun and the cops arrive. Arjun finds Reshma's body and breaks down, feeling guilty and responsible for her death.
Dheeraj targets Priya next whom she calls for a photoshoot and tries to torture her by removing her dresses and even undergarments, but Arjun saves her, engaging Dheeraj in a fight as police officers show up. They request Arjun not to kill Dheeraj. Dheeraj then plays the tape he recorded when he was torturing Reshma. Hearing Reshma's pleading cries, Arjun, tormented by her death and blaming himself for it, angrily kills Dheeraj, ending his reign of terror once and for all.
The film ends with Arjun visiting a church with Priya, implying that Priya's near death has made Arjun realise his love for her.
