In the Indian village of Cinemapatti, male infanticide is predominant, and all male babies are required to be killed immediately after birth. One such baby is headed for such a fate, until he "speaks" to his caretaker-grandmother (Paravai Muniyamma) and asks to be sent to Chennai on a goods train, where he plans to grow into a hero. The old woman complies, and takes the baby, named Shiva, to Chennai and raises him herself, living in the city's poorer section.

On growing into manhood, Shiva (Shiva) gains a reputation by giving a massive entry by beating up extortionists by throwing them in the air and saving a rape victim; soon he is glorified as a "mass hero".[a] He manages to defeat gangster Devaraj with a clever exchange of puns and a costumed associate. He spends his time hanging out, drinking and playing carrom with his gang of friends, composed of Nakul (M. S. Bhaskar), Bharath (Venniradai Moorthy) and Siddharth (Manobala).

Shiva runs into a headstrong girl named Priya (Disha Pandey) whom he falls in love with. After learning of her hatred for men, he realises that she has dedicated her life to classical dance, learns Bharatanatyam over the course of a night, and performs an exaggerated dance sequence for her. She reciprocates his feelings, and the two start a relationship. Shiva is then challenged by Priya's rich and powerful father Kodeeswaran, who refuses to give his daughter to a poor man. Shiva swears to become a billionaire, and promptly does so, during the course of a 2:50-minute song.

Kodeeswaran accepts Shiva as a suitor, and fixes his engagement to Priya. During the ceremony, Shiva hears a passing comment that he does not know his own father. Offended, he travels to Cinemapatti, accompanied by Bharath, to learn his roots. After encountering a host of Tamil-cinema stereotypes of several decades ago, he succeeds in uniting with his family when a woman (revealed to be Shiva's father's concubine) leads him to his father, mother and sister. He finds them when they sing their "family song" (the Michael Learns to Rock number, "Someday").[5]

However, unknown to anyone, Shiva has been targeting and killing several criminals in secret; he kills female gangster Swarna by making her slip over a banana peel; makes another big-time crook laugh to death; tortures a drug dealer to commit suicide by continuous failed attempts on his life; and kills his final victim with the odour of his sock. The police discover that he is the killer, and it is revealed that Shiva is actually an undercover officer and was killing the criminals under direct orders from not only the Commissioner, but also from the President of the United States.

The ganglord who commandeered the slain criminals, a mysterious person simply called "D", organises the kidnapping of Priya by telling Pandian (Sathish), and his henchmen to kidnap her and has Shiva beaten up. Shiva recovers, saves Priya by fighting off thugs using exaggerated stunts, and comes face to face with "D", revealed to be his grandmother. She explains that she did it to increase the fame of her grandson, and a heartbroken Shiva is forced to arrest her.

At the trial, Shiva accidentally kills an assassin who targets his grandmother, and is put on trial himself. He is saved, however, when a man who had helped him in Cinemapatti earlier testifies that Shiva was a victim of circumstance. Both Shiva and "D" are pardoned, and Shiva who has been promoted to DGP, unites happily with Priya, his family and friends.