The film's musical score and soundtrack are composed by Clinton Cerejo and Vishal–Shekhar respectively, with cinematography handled by Setu and editing done by Namrata Rao.

Vidya and Rana break into the NDC office and find Damji's file, barely escaping an encounter with Bob, who is searching for the same information.

Meanwhile, the attempts to obtain Damji's records have attracted the attention of two Intelligence Bureau officials in Delhi—the chief Bhaskaran K. and his deputy Khan.

An errand boy from the neighbourhood tea stall identifies R. Sridhar, an NDC officer, as a frequent visitor to Damji's flat.

Damji cuts the meeting short when Vidya expresses her doubt that he will be able to return her husband in exchange for the sensitive file, and he attempts to leave.

Vidya disarms him using the prosthetic belly she has been using to fake her pregnancy and promptly stabbing him in the neck with her hairstick before finally killing him with his own gun.

She flees into the crowd before the police arrive, leaving a thank-you note for Rana and a pen drive containing data from Sridhar's computer, which leads to Bhaskaran's arrest.

He had to approach several producers to finance him for Kahaani, but was refused[11] and discouraged from making the film owing to three factors: a pregnant woman as the lead star, a bunch of unknown Bengali actors as the supporting cast and Kolkata as a backdrop.

[13] Ghosh finally selected Kolkata for several reasons: the director's acquaintance with the city, its mix of modernity and old-world charm,[13] and budget constraints.

[14] Ghosh admitted in an interview that after his two preceding directorial ventures—Aladin and Home Delivery (2005)—performed poorly at the box office, Kahaani was his last chance to create a niche as a director.

[20][21] The role of the Inspector Satyoki "Rana" Sinha was first offered to Chandan Roy Sanyal, but he could not take the part due to other commitments.

[22] Parambrata Chatterjee, a Bengali actor whose acting in the film The Bong Connection (2006) had impressed Ghosh at the Mumbai Academy of the Moving Image festival, was later offered the role in Kahaani.

[11] Filming took place on the streets of Kolkata, where Ghosh often employed the art of guerrilla filmmaking (shooting in real locations without any previous knowledge given to onlookers) to avoid unwanted attention.

[34][35] The cinematographer Setu, who had assisted others in the past to shoot documentaries in Kolkata, said that unlike majority of Indian films, Kahaani was shot mostly without artificial light.

[43] After Ishqiya (2010), No One Killed Jessica (2011) and The Dirty Picture (2011), Kahaani was Vidya's fourth woman-centric film to win widespread praise for her unconventional approach to portraying strong female roles.

The director explained that the boy was initially "fascinated by someone who is literally a hero in his eyes", as Rana was awed by the computer skills of Vidya.

[52] A review in Rediff.com notes that the director pays a "fond yet understated tribute" to the city by incorporating imagery such as "yellow taxis, leisurely trams, congested traffic, claustrophobic metros, dilapidated brick houses, tapering alleys, rajnigandhas,[c] lal paad saris,[d] piping hot luchis".

[e] According to the reviewer, Kahaani did not depend on the tropes of Kolkata culture typically used in Bollywood film—"O-emphasizing accent, dramatic play of conch shells, rasgulla/mishti doi excesses.

[58] According to Uddalak Mukherjee of The Telegraph, "Durga Puja, with its paraphernalia of idols, immersion processions, pandals, even an entire crowd of women draped in white saris with red borders, is central to the film's ... visual aesthetic.

[61] Ghosh writes that the film was heavily influenced by the colour scheme of the Pratima Visarjan, a c.1915 watercolour by the Bengal School artist Gaganendranath Tagore.

[69] On 5 March 2012, prior to release, Kolkata Metro authorities objected to a scene in which Vidya is pushed by a man onto the tracks as a train arrives.

"[93] Russell Edwards, the reviewer for Variety, praised the cast, cinematography, and direction, and commented that despite occasional glitches, the "adroit thriller ... maintains momentum and credibility.

Rituparna Chatterjee of CNN-IBN noted that the climax of the film was a "huge dampener" and explained, "The diabolic twist at that juncture got underplayed ... What follows is a sobfest ... the apologetic explanation of why she does what she does.

[95] The Outlook review noted, "At times, Kahaani is too clever, at others extremely pedestrian like in the depiction of computer hacking and IB operations, not to speak of the ludicrous terrorist angle and the all-too predictable Durga Puja setting for that mythology tie-in.

"[56] Though Kahaani received critical acclaim, it was a slow starter at the box office, opening to a poor response on the first day,[98][99] but gradually picking afterwards.

[104] The film was successful in the international box office as well, garnering ₹80 million (US$920,000) within 10 days of its release in seven markets—UK, US, UAE, Australia, New Zealand, Malaysia and Pakistan, according to Bollywood Hungama, a film-related website.

[115][116] An English-language remake, entitled Deity, will be directed by the Danish director Niels Arden Oplev and produced by Yashraj Films, with production scheduled to begin in 2015.

[118][119] They felt the landscapes of Mumbai and Delhi were overused for several decades, while Kolkata retained its unique visuals such as metro trains, rickety trams, hand-pulled rickshaws, dingy bylanes, palatial mansions, dilapidated houses of North Kolkata, roadside eateries, ghats of river Ganga, British-era buildings, restaurants and iconic structures and areas including Howrah Bridge, Kalighat Temple, Nakhoda Mosque, Kumortuli idol-making district and Victoria Memorial.

[121] Several hundreds have visited it since the film's release, to the extent that the owners planned to increase tariffs and renovate the rooms around a Kahaani theme.

[43] The potbellied contract killer Bob Biswas became an Internet phenomenon, the subject of several jokes and pieces of pop art, which circulated through Facebook and Twitter.