Sanjay (Emraan Hashmi), a suave, master safe cracker lives with his wife Neetu (Vidya Balan) in a casual lifestyle, and is constantly phoned by his mother, to which he replies that he will speak to her some other time. Sanjay is offered the chance to commit an audacious heist with two dangerous criminals, Pandit and Idris. The bank robbery will ensure that he never has to worry about money again, so he consequently accepts the offer. Together, the three clean out a bank vault and make off with a large sum of 35 crores. While his criminal associates lie low until the heat dies down, Sanjay hides the ill-gotten gains. When Pandit and Idris retu for their share, they find that Sanjay has apparently lost his memory and may be suffering from amnesia. To make sure they're not being ripped off, the two men move in with Sanjay and until he remembers where he hid the money.
Sanjay soon suspects Neetu of knowing the hide-out of the money and conspiring with his friend Uttam Nagpal (Parvin Dabas) when he leas that his friend has become an oveight millionaire by apparently winning an lottery and upon his confrontation has moved to London. Furthermore, Sanjay meets up with a real-estate agent, who had shown him a flat and reveals to him that Neetu and Uttam were seeing an even bigger flat than what he intended to sell them. Soon enough, he finds an one-way ticket for London was bought by Neetu. In midst of all this, an unknown person contacts Sanjay and was him to stop acting and divulge the location of the money. Under pressure, Pandit and Idris kidnap Neetu and ask Sanjay to come to a train station, on the third bogey at 1am. As both Pandit and Idris confront Sanjay to give them the money, Sanjay claims he doesn't even recognise the two.
Following an argument between Sanjay and Neetu in which Sanjay demands that she knew where the money was, Idris begins to lose his mind, and as soon as he pulls his gun out, he is shot by Baba (Shashank Shende), an unknown man sitting at the back of the train. He reveals himself to be the same unknown person who called Sanjay earlier. It tus out, he was the original master of the plan and wants his money under any circumstances. In a rage, he kills both Pandit and Idris. Sanjay tries to battle Baba with his weapon: a dinner fork (on which Baba meekly laughs). Upon persistent questioning and blackmailing, he shoots Neetu, hoping that the traumatic vision of his wife suffering, Sanjay will reveal the truth. However, it fails, as it appears that Sanjay has truly lost his memory and can't remember. He searched Sanjay's pockets, only to find his second weapon: a banana. In retribution, he shoots them both non-fatally and leaves the train.
Sanjay's phone rings and upon picking up, realises its his mother on the line. Sanjay completely forgets his identity and doesn't recognise his mother, to which his mother replies by saying that she has still got an suitcase that Sanju gave her to keep 3 months ago, and if he doesn't come soon, she'll give it to the junk/scrap dealer, revealing that Sanju's mother had the money all along. As the trains starts, Baba overhears this and jumps on the train but slips on Sanjay's banana and got his neck impaled by Sanjay's fork. Sanjay, all bereft, confused and tired, throws his phone out of the train, whilst Neetu smiles. Sanjay has no idea what's going on, and the train continues on riding with the dead bodies of Baba, Pandit and Idris.