Vikram, Suresh Gopi, Amy Jackson, Santhanam, Srinivasan
A. R. Rahman
Lingesan (Vikram) is a bodybuilder from the suburbs of Chennai, whose main ambition is to become Mr. India. He wins the title of Mr. Tamil Nadu, which gives him entry to the Mr. India pageant. He is infatuated by Diya (Amy Jackson), a leading supermodel. She is soon blacklisted and all her advertisement film contracts are cancelled by popular model John (Upen Patel), Diya's co-star in all her advertisements, after she had constantly refused to have sex with him. To save her career, Diya decides to replace John with Lingesan, whom she had earlier met at one of her shoots, as her co-star for her next advertisement. Lingesan agrees, sacrificing his Mr. India dreams in the process.
Lingesan is given a makeover by Diya's stylist, a transgender woman Osma Jasmine (Ojas Rajani). The shoot initially does not go well as Lingesan is shy and awkward around Diya. On her director's advice, Diya pretends to fall in love with Lingesan so that he would loosen up and perform better during the shoot. The plan proves successful and gradually both take the modelling world by storm as the lead pair. As time passes, Diya reciprocates Lingesan's love for her and they soon get engaged.
In this journey from a bodybuilder to a top model, Lingesan makes many enemies, including John, whose modelling career was ruined due to Lingesan's rising popularity, forcing him to appear in local advertisements to stay afloat; Osma, who was infatuated by Lingesan and proposed to him, only to be rejected; a wealthy industrialist Indra Kumar (Ramkumar Ganesan), whose company suffered losses when Lingesan refused to endorse their soft drink as it was reported to contain pesticides; and another bodybuilder Ravi (M. Kamaraj), who also competed for the Mr. Tamil Nadu title but lost to Lingesan. These four people conspire to take revenge on Lingesan and destroy his fame and modelling career.
Two days before his wedding, Lingesan slowly starts to experience hair and teeth loss and a skin disorder. He consults his friend Dr. Vasudevan (Suresh Gopi), who is also the guardian of Diya's family. Vasudevan informs him that he is suffering from a rare and incurable genetic disease which results in premature ageing. Lingesan's condition worsens, with his face and body deforming, and eventually he becomes a hunchback. In his current condition, Lingesan decides to disappear from public eye by faking his death in a car accident. Only his close friend Babu (Santhanam) and Vasudevan know that he is alive. Lingesan asks Vasudevan to marry Diya as he is the only person who will be able to understand Diya's past and present situation. Vasudevan reluctantly agrees and the wedding is fixed.
On the eve of the wedding, Lingesan learns from another doctor that he is not suffering from an incurable genetic disease but from a disease called H4N2 influenza, caused by the "I" virus, which can only be transmitted by injection. He discovers that John, Osma, Kumar, Ravi and, to his horror, Vasudevan, are responsible for injecting the virus into his body. Vasudevan had an insatiable lust for Diya since she was a teenager and was enraged when she chose Lingesan over him. As a result, he sided with Lingesan's enemies and planned the entire operation to get Lingesan injected with the I virus. Enraged and betrayed, Lingesan abducts Diya on her wedding day and keeps her safely in an old house without revealing his identity to her.
Aided by Babu, Lingesan starts taking revenge on those who had deformed him. He first immolates Ravi, who suffers severe burns. He then prepares a paste which Osma applies on her body, causing her body to sprout huge growths of hair. Next, he subjects Kumar to bee stings all over his body. He fights John over a moving train and gets him electrocuted. Finally, he gets Vasudevan to unwittingly inject a deadly virus into himself, causing his whole body to swell up. After he has avenged those who ruined him, Lingesan reveals his condition to Diya, who, though initially taken aback, still loves him despite his deformity. They decide to live a secluded life together. Lingesan undergoes ayurvedic treatment for his condition and eventually returns to his normal self.