Kahaani 2

A poison gas attack on a Kolkata Metro compartment kills all passengers aboard, instantly turning a routine commute into a citywide tragedy. The incident becomes the catalyst that motivates Vidya's search and reveals a web of secrecy behind Arnab's disappearance.

Vidya Bagchi, a pregnant British-Indian software engineer, arrives in Kolkata from London during the Durga Puja celebrations to look for her missing husband Arnab Bagchi. She seeks help from a police officer, Satyoki 'Rana' Sinha, and begins to press her inquiry.

Rana offers to help Vidya, and the investigation quickly centers on her case. The initial probes suggest Arnab did not work for the National Data Center, complicating Vidya's search.

Agnes D'Mello, head of HR at the NDC, hints that Arnab may resemble a former employee named Milan Damji whose file is stored in the old records. Before she can share more, Agnes is killed at her doorstep by Bob Biswas, an undercover assassin.

Vidya and Rana break into the old NDC office and locate Damji's file. They uncover Damji's link to Arnab and the gas attack, and narrowly escape Bob, who is dispatched to seize the information.

Two Intelligence Bureau officials, Bhaskaran K. and Khan, arrive and reveal that Damji was a rogue IB agent connected to the poison gas attack. Khan's warnings only harden Vidya's resolve to uncover the truth.

Their investigation leads to a dilapidated flat where an errand boy from a nearby tea stall identifies R. Sridhar, an NDC officer who frequents Damji's flat. A chase ensues and Bob makes another attempt on Vidya's life but is run over during the pursuit.

Sridhar's computer data yields a decipherable code that leads to Bhaskaran's phone number. Vidya reaches Bhaskaran and offers to trade Sridhar's data for help locating Arnab, but Bhaskaran redirects her to the local police, raising the stakes.

A mysterious caller warns Vidya that she must surrender the documents to stay alive, and Khan suspects the caller might be Damji. The pressure mounts as Vidya presses on with the lead.

Vidya, Rana, and Khan converge on Damji. Damji tries to flee, but Vidya disarms him using a prosthetic pregnancy belly and stabs him with his own gun, then disappears into the crowd. She leaves a note for Rana and a pen drive containing Sridhar's data that helps trap Bhaskaran.

Rana concludes that Vidya and Arnab never truly existed and that Vidya has been manipulating the police and IB networks to further her aims. The truth about Vidya's husband’s identity is then revealed: she is the widow of Major Arup Basu, an IB/Army officer who died in the same gas attack.

Col. Pratap Bajpayee, a veteran IB officer, helps Vidya in her mission. The film closes with Vidya's resolve intact, shaped by memory, loss, and a determined will to uncover the truth behind the attack.