Kahaani is a 2012 Indian thriller film directed and co-produced by Sujoy Ghosh. It stars Vidya Balan, Parambrata Chatterjee and Nawazuddin Siddiqui in lead roles. Balan portrays the role of Vidya Bagchi, a pregnant woman in search of her missing husband, who is helped in her quest by Chatterjee and Siddiqui. After starring in strong female-oriented films like Ishqiya, No One Killed Jessica and The Dirty Picture, Kahaani was Balan's fourth consecutive film to win her critical acclaim.
Kahaani was released on 9 March 2012 to wide critical acclaim and emerged as a "Super Hit" at the box office. 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 the period of preparation for the Durga Puja. She is looking for her missing husband Arnab Bagchi and is offered support from Satyaki Sinha/Rana (Parambrata Chatterjee), a junior police officer from Kalighat Police Station. Although Arnab came to Kolkata on an assignment for the National Data Center (NDC), initial probes suggest that no person named Arnab Bagchi came to work in NDC, or stayed in the guesthouse that Arnab had described to Vidya during their phone conversations.
Agnes D'mello, head of human resources at NDC, suggests to Vidya that her husband resembled Milan Damji (Indraneil Sengupta), an ex-employee of NDC. She told Vidya that she would try to obtain his records from NDC's old office. Before she could do so, however, Agnes is killed by Bob Biswas (Saswata Chatterjee), an assassin who works undercover as a life insurance agent. Vidya, assisted by Rana, breaks into the old office of NDC to collect documents on Damji. They barely manage to escape a close brush with Bob who was also looking for the documents.