The film opens in a rundown pigeon shop in New York City where an old man feeds them. He then sends one pigeon away. It flies high and lands in a skyscraper off the office window of a psychologist who is conducting a session with her client Nirupama (Pooja Kumar), a nuclear oncologist, who begins to confide that hers was a marriage of convenience that provided a safe haven for pursuing her PhD in the U.S.A. for past three years and that her husband Vishwanath alias Viz (Kamal Haasan) is a middle-aged Kathak teacher. She is also put off by Viz's effeminate bearing and is attracted to her boss, Deepankar (Samrat Chakrabarti). Doubting whether her husband has secrets of his own, she hires a private investigator to tail him to probe grounds for divorce. She learns from the private investigator that Viz is a Muslim. In a sudden turn of events, the investigator is killed in a sea-side warehouse by Farukh(Mukhtar Khan), a prominent member of the terrorist outfit led by Omar (Rahul Bose). A diary on him gives away Nirupama and the terror group led by Farukh nabs the couple. Deepankar is later killed by Farukh's men.

Viz surprises Nirupama by having a fight with the terrorists, kills Farukh and his men at the warehouse and escapes with Nirupama. Omar and Viz have a past, one that takes the story back to circa 2002, to the Al-Qaeda training camps in Afghanistan-Pakistan border. Viz's real name was Wisam Ahmad Kashmiri. He claims to be a Tamil Jihadi in Kashmir, wanted by the Indian Army, with a reward of ? 500,000 on his head. Omar accepts him into his team and drives him off to Afghanistan. Wisam becomes a trainer to the Al-Qaeda Jihadi's and also a family friend to Omar. One day, Omar tells Wisam that American prisoners of war are still alive, incarcerated and shifted each fortnight. He orders his deputy Salim (Jaideep Ahlawat) to behead the Captain and capture it on video. The next day, Salim tells Wisam that a new tall guest is expected in the town. Wisam later that night sees Osama bin Laden (Naren Weiss) greeting the Al Qaeda chieftains in a cave. Then, a joint US-led air force begins a bombing raid on the town. Omar begins to doubt that there is an informer in the team but mistakenly orders lynching of an innocent man. What follows is a maze of events that go back and forth in time, unraveling a plot where in the terrorists are scraping cesium from oncological equipment to build and trigger a dirty bomb in New York City.

Nirupama is stunned to discover the true identity of Viz, his "uncle" (Shekhar Kapur), British "friend" Dr Dawkins (Miles Anderson) and the young "dancer" Ashmita (Andrea Jeremiah). Viz later reveals that he has a lot of emotional baggage and that he had executed many terrorists including Nassar (Nassar), Omar's boss. His mission is to bust the sleeper-cell of Al Qaeda in the US, which is planning to divert the attention through "capsules" capable of emitting mild nuclear radiation tied to pigeons while enabling Abbasi, a Nigerian suicide bomber to detonate the cesium dirty bomb in the city.

Together, the Wisam team try to counter the plans of Omar. In the ensuing events, Wisam is arrested by the FBI before being rescued by his "uncle" Colonel Jagannath and Dr Dawkins is murdered by Salim while picking up a video tape from an antique shop. The FBI later releases Wisam after a call from the Indian embassy and Prime Minister of India, where the true identity of Wizam is revealed as an agent of Research and Analysis Wing (RAW), India. Wisam along with the FBI, take down Abbasi and defuse the Cesium bomb with the help of Nirupama by using a microwave oven as a Faraday cage to avoid incoming calls from any mobile phone. Omar and Salim try to escape in a plane. Omar tries to activate a bomb through his phone, but fails. He then calls Abbasi, but call is answered by Wisam, who tells him that Abbasi is not alive. Omar is shocked to hear this but escapes with Salim in his plane. The film ends with Wisam indicating that he would now go after Omar, alluding to a sequel set in India.

• Kamal Haasan as Vishwanath / RAW agent Major Wisam Ahmad Kashmiri
• Rahul Bose as Omar Qureshi
• Shekhar Kapur as Colonel Jagannath
• Pooja Kumar as Nirupama Wisam aka. Nirupama Vishwanath
• Andrea Jeremiah as Ashmita Subramaniam
• Jaideep Ahlawat as Salim
• Samrat Chakrabarti as Deepak Chatterjee
• Nassar as Nassar, Omar's boss
• Zarina Wahab as the psychiatrist
• Miles Anderson as Dawkins
• Mukhtar Khan as Farrukh
• Naren Weiss (as Nareen) as Osama bin Laden
• James Babson as Tom Black
• Jude S. Walko as Captain Joe Black
• Chris Kotcher as Tollbooth Operator
• Greg Sammis as F.B.I. Agent
• David Scott Diaz as F.B.I. Agent

Development

After finishing his Manmadan Ambu (2010), Kamal Haasan stated in November 2010 that he was working on the scriptment of his "pet project" titled Thalaivan Irukkiran, a film about an international community. Termed as a big budget multi-starrer film, it was expected to commence by March 2011, with a Hollywood studio reportedly coming forward to produce it. However, in early 2011, sources claimed that Kamal shelved that project and agreed to star in a Selvaraghavan directorial, being impressed by the one-line story narrated to him. Reports further suggested that the film was based on the 2001 American psychological thriller Hannibal, with Kamal playing a cannibal, Closer to release, Kamal Haasan revealed that he had thought of the story seven years before production began and had to convince himself that the story could be made into a feature film. The film was named Vishwaroopam, after several titles were considered, by late March and the shooting was planned to begin by mid-April and to be completed within 100 days. It was revealed that the film would be produced in three languages—Tamil, Telugu and Hindi—simultaneously.

On 24 May 2011, it was announced that Selvaraghavan was ousted from the project, as he was busy finishing his project with his brother Dhanush. Kamal Hassan decided to direct the film himself in addition to writing the story, screenplay and dialogues. The producing studio, Telephoto Films, had urged him to take up the project, planning for a release on 7 November 2011,. The film was then disclosed to be a spy thriller on the lines of the Mission Impossible series. The film was being made as a bilingual and simultaneously shot in Tamil and Hindi languages; all the actors had to learn their dialogues in both languages. Sanu Varghese made his debut as a cinematographer in Tamil after previously working in the Hindi film, Karthik Calling Karthik and the Malayalam film Elektra. Varghese had previously been a part of the team that Kamal Haasan had assembled for Marmayogi, which did not take off. Mahesh Narayanan, a leading Malayalam film editor, was signed up for the project after he had acquainted with Kamal Haasan for the pre-production works of the film Traffic, which the actor later opted out from. The team signed up N. G. Roshan as a make-up artiste after Kamal Haasan appreciated his work in the 2009 Malayalam film Pazhassi Raja, while Mahadevan Thampi was picked to be the still photographer after Kamal Haasan had worked with him for a day during his guest appearance in Four Friends.

Casting

By February 2011, newcomer Sonakshi Sinha was approached to play the lead female character, and was confirmed to play Haasan's wife. Her salary for the film was touted to be ?20 million (US$300,000). However, with the film getting delayed, she opted out by July, due to conflicting dates with her Hindi assignments. Following Sinha's exit, other leading Bollywood actresses, including Katrina Kaif, Deepika Padukone, and Sonam Kapoor were considered. Vidya Balan was also approached by the makers, but she declined the offer, owing to her prior commitments. By mid-August, Sameera Reddy was reported to have been roped in for the role, while sources stated that Anushka Shetty was finalised soon after. In early November 2011, New York based model-actress Pooja Kumar was signed in for a role after she had been recommended to Kamal Haasan by his partner, Gouthami. The i