In Kalimpong, Maya D'Souza (Kareena Kapoor Khan) is a divorced, single mother who works at a cafeteria. Naren Vyas (Jaideep Ahlawat) is a reclusive, but brilliant mathematics teacher, who lives next door to Maya and Tara (Naisha Khanna) (Maya's daughter). Through a gap in the wall, Naren can peep into Maya's apartment and see everything that is going on in their lives.Naren is solemn and introverted, and his morning exchanges with Maya from whose cafeteria he buys lunch, is the brightest part of his day. Maya's colleague at the cafeteria tells her that Naren only comes to the cafeteria when Maya is at the counter. She says that Naren has a crush on Maya. Ajit (Saurabh Sachdeva), Maya's abusive ex-husband, shows up one night to extort money from Maya, threatening both her and Tara. Ajit has found Maya after 14 years and it is implied that Maya is not her real name, she had changed it from Soniya to protect her whereabouts from Ajit. Ajit follows Maya home, who gives him whatever little money she has. Maya wants Ajit gone as soon as possible. Ajit wants to take Tara and push her into the prostitution business, just like Maya was before. The situation quickly escalates into violence and Ajit is killed by mother and daughter on the apartment floor.Overhearing the commotion from his room and deducing that Ajit has been killed, Naren offers his help to the mother and daughter. He not only disposes the body, but also plots the cover-up step-by-step. The evidence shows that Maya strangled Ajit with a wire, while Tara grabbed his hands by her nails, so he could not save himself. He sanitizes the heating rod wire that was used to kill Ajit and also the entire apartment. Ajit was staying at hotel Alice Villa, and had paid for 3 days, 2 days ago. So, Naren says that they have 1 day before his absence is reported. Naren says that since Ajit was in the police, someone will come looking for him. Naren asks Maya and Tara to create an evidence trail for themselves.When the body turns up and is identified, Inspector Karan Anand (Vijay Varma), who was initially investigating the disappearance of Ajit and happens to be the former classmate of Naren, draws the case and Maya comes under suspicion. Ajit was suspected to be a major money launderer for the mafia and was in the police himself. A strip club owner tells Karan that Ajit had come in a week ago and was talking about a lottery in Kalimpong. Karan reaches Kalimpong and has coffee at Maya's cafe. Maya says that she has not seen Ajit.Karan finds Ajit's luggage in hotel Alice Villa. He finds that Ajit was looking for a school. Karan finds Maya there talking to Tara. Karan checks out Maya's connection to Ajit. Naren tells Maya that Karan will come for her. Naren asks her to pretend that Ajit is still alive. He says that Ajit's body will never be found. Karan finds a deeply charred body in the jungle with Ajit's ID next to it. The body has no fingerprints or teeth. The body had traces of blood on the clothes, and blood matches DNA samples picked from Ajit's room. Karan concludes that the body belongs to Ajit. He died at around 7 pm.Karan meets Maya at her house and this time she says that Ajit was her husband. She doesn't want Ajit anywhere near her daughter. She says Ajit came to Kalimpong to ask her for money. Maya says that Ajit married her and then sold her to Paradise strip club. Maya says that on the day of Ajit's murder at 7 PM she was watching a movie at Capitol Cinema with Tara. They had dinner after that, and then Karaoke. They left home around 5:30 PM and returned at 11 PM.Karan is unable to find any obvious holes in Maya's manufactured alibi, but he is still sure that there is something wrong with her alibi, a suspicion that he cannot shake. Karan says that the night of the murder was Thursday and Tara had school the next day. Why would Maya keep her out till 11 PM in that scenario. Karan questions Tara as well, but she was also well prepared by Naren. Naren never mat Maya or Tara in person, but kept in touch with them on their landline, via a payphone outside his Dojo.Karan finds out that the dead body had strangle marks on the neck and blunt injury at the back of the head. His colleague says that both injuries look like that from a coil water heater. Karan lures Maya out of the house and his colleagues enters the house behind her to take the coil heater for analysis. But the coil heater does not match the patterns found on the dead body. It is not the murder weapon.Karan is about to close the case and leave Kalimpong, when he learns from Maya's colleague at the cafe that Naren is Maya's only friend in the city. Naren had hidden this information from Karan. Naren was on leave on the day of the murder. For the first time in 10 years of service. Karan is convinced that Naren had something to do with the murder, leading towards a dangerous cat-and-mouse game between the two. Karan tries to rile Naren by implying that Karan had a mutually lustful connect with Maya. But Naren plays it cool. Naren meets Maya and tells her to stay out of the matter, no matter what happens.The next day Naren admits to Karan that he killed Ajit. He says that he is Maya's bodyguard and he killed Ajit because he knew never wanted to see him again. Naren described step by step how he lured Ajit to an isolated area, strangled him, bashed his face and burnt his body. Naren is adamant that Maya was asking for his help through the gap in their walls, while she was pretending to talk to Tara. Naren appears as mentally deranged. Maya, of course, says that she knows nothing. Naren says that he is revealing all this as Maya betrayed him with Karan. Karan finds the murder weapon in Naren's bathroom. His internet search history had instructions on how to dispose a body.Towards the end, both Naren's scheme and the reason for his devotion to Maya are revealed: Naren had lost his will to live due to his depression and was prepared to commit suicide when he was interrupted by Maya introducing herself, leading him to become deeply attached to her and thankful for her unknowingly saving his life. Naren had solved a math problem after 10 years of hard work and then found that someone else had solved it 2 days ago. This was the reason for his depression and attempted suicide.In order to deceive the investigation, Naren murdered a second person, a homeless man who he had seen prior on his commute to work, and made the police believe he was Ajit, in order to obfuscate the date and time of the murder by 24 hours and make it so that in the end he could take the fall.Naren eventually confesses to the crime to protect Maya and pretends to be mentally unstable. He is imprisoned and he spends his time in prison solving a complex mathematics problem.