‘Ghanchakkar’ is about a Maharashtrian thief, married to an aggressive Punjabi woman, who carries out a bank heist. Before he can spend the loot, he meets with an accident. Will his memory and money come back to his use?

It starts with Sanjay (Emraan Hashmi), a master safe cracker who maintains a casual lifestyle with his wife Neetu (Vidya Balan). He is offered the chance to assist with a bank robbery alongside two criminals, Pandit and Idris. The three thieves make off with 350 million rupees. While his associates lie low until the heat dies down, Sanjay hides the money, but when Pandit and Idris return for their share, they find that Sanjay has apparently lost his memory. To make sure they're not being cheated, the two move in with Sanjay until his memory returns.

An unknown person contacts Sanjay and urges him to divulge the location of the money. Under pressure, Pandit and Idris kidnap Neetu and ask Sanjay to meet them in a train station, on the third platform at 1am. When both Pandit and Idris confront Sanjay and demand the money, Sanjay claims that he doesn't even recognise the two. When Sanjay says that she knew where the money was, Idris begins to lose control. When he pulls his gun, he is shot by Baba (Shashank Shende), an unknown man sitting at the back of the train. Baba reveals that he is the unknown person who called Sanjay earlier. It turns out that he was the person who originally devised the plan and now wants his share. Sanjay tries to defend himself with his only weapon, a fork. In a rage, Baba kills both Pandit and Idris. After persistently questioning and trying to blackmail Sanjay, Baba shoots Neetu, hoping that the traumatic vision of his wife's suffering will make Sanjay reveal the truth. This fails, however, since Sanjay has in fact lost his memory. Baba searches Sanjay's pockets, only to find his second weapon, a banana. In retaliation he shoots them both and leaves the train.

Sanjay's phone rings and he finds his mother on the line. Sanjay has completely forgotten his identity and doesn't recognise his mother, but she says she still has a suitcase that Sanjay gave her to keep three months ago, and if he doesn't come soon, she'll give it to the junk dealer. Sanjay's mother had the money all along. Baba overhears this and jumps on the train just as it's starting, but he slips on Sanjay's banana and impales his neck on Sanjay's fork. Sanjay, bereft, confused and tired, throws his phone out of the train while Neetu smiles. Sanjay has no idea what's going on, but the train goes on its way with the dead bodies of Baba, Pandit and Idris.