The movie opens with Vetrivel (Vijay) having a happy, rural life in a village. He has a younger sister (Saranya Mohan) and a mother who are very affectionate. His father had passed away a few years ago. Vijay is teased by his Uncle's daughter (Hansika Motwani) who has a big crush on him. She chases him all the time, but Vijay is not in love with her. Satyan is a close friend of Vijay, who hangs out with him. Vijay's main aim is to get his sister married to a good family and get her settled.
The next episode opens in Chennai, which is dominated by Rowdies. Genelia is a writer for a popular daily magazine who struggles with rowdy activities. She has had enough and wants to put an end to the rowdyism in Chennai, but does not know how. As luck would have it, she witnesses some rowdies fall off a mountain top and die. This is an accident, but Genelia decides to take the opportunity to portray a Super-Hero who killed these goons. She creates a character called 'Velayudham' who has arrived to eliminate rowdyism and creates a propaganda. Soon, the general public starts believing the story and expect Velayudham to eliminate rowdyism. Pasupathy is the D.I.G of Chennai, and starts trying to find Velayudham.
Vijay's sister Saranya Mohan, falls in love with another village boy. They both are caught red handed by Vijay. Vijay tells the boy to bring his parents and ask for a conventional wedding. Both the sides agree for the wedding and Vijay needs to get the money from the finance company in Chennai. He has been saving money and depositing in the finance company for many years, for his sister's wedding.
Vijay comes to Chennai to get the money, however he accidentally lands on a bomb waiting to explode in a public place. The place is full of innocent children, women and old people. He removes the bomb from the place and saves the people. He catches the rowdy who planted the bomb and realizes there are 5 more time bombs planted all over Chennai. He removes each and every bomb, and saves the city of Chennai. Because of this great feat, people think that he is the Super hero 'Velayutham'. Genelia quickly approaches Vijay and asks him to take the role of the Super Hero. Vijay refuses, as he wants to go back to his village and get his sister married. He also becomes friends with Santhanam, who lives in Chennai. The next morning, Vijay goes to the finance company, and realizes that it is a fraud. The company had cheated a lot of innocent, poor people of their hard earned money. Vijay sees a mother of a young girl commit suicide and decides to take revenge on the person who is responsible for this. To do this, he dons the role of the super hero "Velayutham" . In the mean time, Genelia falls in love with him.
KrishnaDeva (Omi Vaidya) is a very religious Hindu, who lives as a saint, but is behind all the corruption, counterfeiting, Bombing in Chennai. The general public believes that he is a very religious Hindu and lives by the Hindu principles. In reality, he is a Muslim terrorist, who is trying to disrupt India, by these activities. Omi Vaidya is already angry because Vijay removed all the bombs he planted. Now both of them come to stand off, and one of them should die. What happened next? Did "Velayutham" get rid of terrorism? Was his true identity revealed to the public? What happened to Genelia?