The story follows Sonu Dilli (Emraan Hashmi), a street-smart, small time arms dealer in Delhi who has the gift of gab. When he is interrogated by a tough cop, ACP Pratap Raghuvanshi (Randeep Hooda), he turns informer for the latter. Although helping Pratap puts Sonu in jail for a little time, he continues to purvey the ACP with information about illegal arms racket as he has no other choice. But when Sonu falls in love with Dr Jhanvi (Esha Gupta), and manages to woo her, he wants to leave the life of crime and settle down. However, Pratap, who is hell bent upon finding who the leader of the arms racket is, persuades Sonu to continue being his informer by promising him protection and a good life afterwards.
Sonu's world is shaken to the core when he realises, after his marriage to Jhanvi, that Jhanvi's estranged father, Mangal Singh Tomar (Manish Choudhary), is actually the leader of the guns/arms business in Delhi. Soon enough, Sonu becomes a police informant for ACP Pratap, who has been looking for Mangal. Becoming a police informant, Sonu manages to convince Mangal that he is a corrupt and shrewd person who will be of use to his gang. Mangal embraces Sonu as his next in command. Sonu, caught between the devil and the deep sea, starts playing a double game. He neither gives information to the ACP, nor tells Mangal the truth about him being a police informer. Secretly he plans to run away with Jhanvi, so that he can live a peaceful life with her. However, things get risky once a mysterious informer in the police force tells Mangal about Sonu's truth.
During a shootout, Mangal finds out the truth about Sonu, and takes his whole gang after him. Sonu, on the run, rings ACP Pratap for help. Pratap then brings his whole police force to the scene. There, Sonu is surrounded by Mangal's gang, which is then gunned down by the police chief commissioner. With only Sonu, Mangal and the chief left, it turns out that the chief is actually Mangal's informer, and they both follow Sonu to a deserted area. There, Sonu meets Pratap and tells him he is done and leaves to go to his wife. However, he is shot by the chief. Pratap, seeing Sonu get killed, shoots the chief commissioner and Mangal multiple times, leading to their deaths.
In the hospital, during Sonu's last words, he tells Pratap that his wife Jhanvi should not know about his death, and Pratap should tell her that he was a criminal who committed smuggling and ran away. After his death, Pratap goes to his house and informs Jhanvi that Sonu ran away from the city. Jhanvi, heartbroken, thinks straight and forgets Sonu, and moves away to carry on life as normal.