Kahaani - Plot

Plot

The film opens with a poison-gas attack on a Kolkata Metro Rail compartment, killing the passengers on board. Two years after the incident, a London-based pregnant software engineer Vidya Bagchi (Vidya Balan) arrives in Kolkata during Durga Puja festivities in search of her missing husband, Arnab Bagchi. A police officer Satyaki "Rana" Sinha (Parambrata Chatterjee) offers her help. Although Vidya claims that Arnab came on an assignment for the National Data Center (NDC), initial probes suggest that no person named Arnab was working in NDC.

Agnes D'mello, the human resources head at the NDC, suggests to Vidya that her husband resembled Milan Damji (Indraneil Sengupta), an ex-employee of NDC. Before Agnes can obtain Damji's records, she is killed by Bob Biswas (Saswata Chatterjee), an assassin working undercover as a life insurance agent. Vidya and Rana break into the old office of NDC to collect documents on Damji. They barely manage to escape a close brush with Bob, who is also looking for the documents. Meanwhile, the attempts to obtain Damji's records rattle two Intelligence Bureau (IB) officials — the chief Bhaskaran K. (Dhritiman Chatterjee) and his deputy Khan (Nawazuddin Siddiqui). Khan arrives in Kolkata and reveals that Damji was an IB agent gone rogue and was responsible for the poison-gas attack. In spite of warnings by Khan, Vidya continues her relentless search, fearing that Arnab's resemblance to Damji has led him into trouble.

The residential address on Damji's record leads Vidya and Rana to a dilapidated flat. An errand boy of the neighbourhood tea stall, Poltu, informs them that the resident of that flat occasionally had a visitor. Poltu identifies R. Sridhar, an officer of NDC, as the person who had visited Damji's flat. This leads Sridhar to instruct Bob to kill Vidya. Following a failed attempt to kill Vidya, Bob is run over by a tempo during a chase. Examination of Bob's mobile phone leads Vidya and Rana to an IP address sending instructions to kill her. They break into Sridhar's office to verify his IP address but Sridhar gets alerted electronically, and returns to his office pursuing the duo. Following a scuffle, Vidya shoots Sridhar accidentally which upsets Khan as he wanted Sridhar alive.

Khan reveals that Rana had been working for him all along, using Vidya as a tool. Although not happy at being used as a ploy, Vidya agrees to help Khan on his request but ignores Rana. Sridhar's computer data reveals a code which is deciphered to be Bhaskaran's phone number. Vidya calls Bhaskaran to tell him that she has retrieved sensitive documents from Sridhar's office and if Bhaskaran helps Vidya find her husband, she would hand over the documents to him. Bhaskaran tells Vidya to contact the local police as he is not associated with this. However, Vidya soon gets a call from an unknown number, warning her that she should hand over the documents to the caller if she wishes to see her husband alive. Khan thinks the caller is Milan Damji.

As instructed, Vidya goes to meet Damji, with Rana and Khan in pursuit. During their negotiations about the documents and the whereabouts of her husband, Damji attacks Vidya hitting her in the abdomen. He points his gun at Vidya to kill her, but is thwarted by the prosthetic abdomen which Vidya has been using to fake her pregnancy. She kills a baffled Damji and flees into the crowd nearby before the arrival of police, leaving a thank-you note for Rana and a pen drive containing data from Sridhar's computer. Rana, based on several past incidences, deduces that no Vidya or Arnab Bagchi ever existed. It is she who has been using the police and the IB for her task. The data from the drive leads to Bhaskaran's arrest. Vidya is revealed as the widow of Arup Basu (Abir Chatterjee), an IB officer and a colleague of Damji, who was killed in the poison-gas attack. In her mission to take revenge of her husband's death, Vidya was helped by retired IB officer colonel Pratap Bajpayee (Darshan Jariwala), who suspected the involvement of one of the top IB officials in the attack.