In 2013, Assistant Commissioner of Police Raghavan Amrendra Singh Umbi, a drug addict, makes visits a Mumbai drug dealer. However, his plan to purchase drugs is foiled - the dealer and another man have been murdered. Investigating the murders the next day, he receives a hammer followed by an anonymous phone call.
In 2015, a man named Ramanna surrenders to the police and confesses killing nine people. He is detained and beaten by the police, but manages to escape with the help of a group of nearby boys. Seeking food at the home of his sister Lakshmi, Ramanna argues with his brother-in-law. After leaving the house he quickly returns and kills the couple and their son. Raghavan is among the police who later investigate the house, where he finds a picture of Ramanna with Lakshmi, confirming Ramanna's involvement in the crime.
Raghavan is in a relationship with Smrutika "Simi" Naidu, but he is an abusive partner: he beats her and has coerced her to have three abortions. Ramanna surveils Raghavan and Simi, suggesting some kind of link exists between the cop and the killer. This surveillance escalates into more murders when Ramanna stalks and kills Simi's maid and her husband. After these killings, Ramanna is caught by the police with assistance from an onlooker. However, Ramanna escapes from custody again and kills the man who aided his capture. Raghavan proves to be a killer himself when, on a trip to visit his father, he murders an African drug dealer.
On a later evening, Raghavan picks up another woman named Ankita at a nightclub and brings her to Simi's house. Incapacitated by his drug use, Raghavan is unable to perform sexually, prompting mockery from Ankita. In response he assaults her. Enraged, he searches for the stash of drugs he keeps at the house, but is unable to find it. In this state he confronts Simi and they argue. When Simi demands he leave with Ankita, he strikes Simi; her fall into a glass table kills her instantly.
Ankita locks herself in the bathroom and tries to call for help, but desists when Raghavan threatens and coerces her. He then clears away incriminating evidence and arranges the scene to implicate Ramanna for the murder. He retrieves a tire iron similar to Ramanna's favored murder weapon and smashes Simi's head with it. During these preparations Ankita escapes.
The next day Ramanna surrenders to Raghavan and claims a deep connection with him: each man is the missing half of the other. Ramanna also reveals his role in the two 2013 murders that opened the film and initiated this connection. He confesses to one of the killings, but witnessed Raghavan kill the other man, and thus began his surveillance of the policeman. Ramanna offers to accept the charge for Simi's murder, but only if Raghavan will kill the eyewitness, Ankita. In the final scene Raghavan's descent into evil matches Ramanna's when he murders Ankita in her home.