Cast: Vijay as DCP Vijay Kumar alias Joseph Kuruvilla alias Dharmeshwar, Samantha Ruth Prabhu as Dr. Mithra, Amy Jackson as Annie Miss, Baby Nainika as Niveditha aka Nivi, J. Mahendran as Vanamaamalai, Prabhu Ganeshan as Commissioner Sibi Chakravarthi, Raadhika as Vijay's mother, and Rajendran as constable Rajendran.
Vijay Kumar is an honest and sincere DCP of Chennai. He takes up a case involving the rape and subsequent death of an IT employee Raji. He finds out that the rapist is Ashwin, the son of Labour Minister Vanamaamalai. Vijay kills Ashwin. He then reveals himself as the murderer of Ashwin to Vanamaamalai. Vanamaamalai swears to take revenge on him for killing his son.
Meanwhile, Vijay falls in love with a medical student Mithra and both eventually get married and lead a happy life. But, Vijay's happiness is short-lived as Vanamaamalai, his younger brother Ratnam and their henchmen barge into his house one night and kill Mithra and Vijay's mother.
They even brutally assault Vijay and attempt to drown Vijay's baby daughter Niveditha aka Nivi in the bathtub. The dying Mithra manages to rescue Nivi and asks Vijay to take care of her, but not before making him promise that he will quit the police job and be a peaceful and loving father to Nivi, following which she dies in Vijay's arms.
Vijay fakes his death, changes his name to Joseph Kuruvilla, maintains a low profile and moves to Kerala with Nivi and his constable friend Rajendran to protect Nivi from Vanamaamalai and his gang. There he starts a bakery with Rajendran and leads a peaceful life. But things go the way for long. After a period of serene five years, Vaanamaamalai does an unthinkable thing. What Vijay does after that and how he avenges his wife and mother's deaths and teach Vanamaamalai a lesson forms the crux of the story.
Theri is well received by the critics and the audience and is recorded as a profitable venture at the box office. Vijay's performance and director Atlee's work as praised.