Dhanush, Trisha Krishnan
For Kodi (Dhanush), politics has been a part of his life ever since his birth. His father Murugan (Karunaas), a low-rung party worker, brings him up to become a politician, before setting himself on fire, protesting against a factory whose toxic mercury waste has ruined lives in the locality. Kodi’s identical twin, Anbu (also Dhanush), is a contrast to his rough-and-tough brother. He is a college lecturer and a pacifist.
Kodi is the secretary of his party’s youth wing and his adopted assistant who is more brother like to him is Bhagat Singh (Kaali Venkat). His girlfriend Rudra (Trisha), who belongs to the ruling party and has been in politics since childhood like him. Here enters egg-seller Malathi (Anupama Parameswaran), whose eggs are broken by Kodi. When she chases him, she comes across Anbu and mistakes him as Kodi. That day, she goes to Anbu"s college for some work and there she sees him and slaps him, takes away his phone and him to return her broken eggs' money and then take it. In between happens series of comical incidents. Anbu falls in love with Malathi. Malathi tells him her village pathetic condition due to the factory's mercury waste, which Anbu tells Kodi.
Kodi soon tells this matter to Thalaivar (S.A. Chandrasekhar), who tells that they would take up this matter. Meanwhile, Kodi comes in possession of documents relating to the factory, from which he comes to know that his party member Marimuthu (G. Marimuthu) and the whole party is responsible for what has happened to the villagers. He angrily tells it to Thalaivar, who tells that it is true. Depressed, he shares this information with Rudhra who speaks up this matter in public, causing great embarrassment to Kodi's party and the party thinks he would not remain silent and this could ruin his party’s chances in the election, and to keep him silent, his party leadership announces him as their candidate. Problems soon arise as Rudhra's party members come to know about the Kodi-Rudhra's affair, and start pressurizing Rudhra to give up her candidacy. A depressed Rudhra is called upon by Kodi to him in the woods. When they meet together, the goons sent by former MLA Arivazhagan (Namo Narayana) of the region, who was dethroned by Rudhra using her tactics, attacks them. Kodi defends them by finishing up the goons but in the end he is stabbed by Rudhra, who tells him that she imagined if he died then there is no obstacle for her. Kodi dies for her sake.
Rudhra meets Kodi's family after funeral and tells them that her party is willing to give Anbu the post of MLA because she became MP of Rajya Sabha. Kodi's mother (Saranya Ponvannan) denies, but Anbu accepts it. Anbu wins the by-election unopposed. Anbu changes his look as Kodi and behaves more like Kodi. His mother tells Rudhra that a Doctor told her that if one of the twins die, than the other one would either wish to die like them or they would like to live the other one's life. Soon, Anbu takes up two matters, first is to find his brother's murderer and the second is to solve the issue of the factory. When he tells Rudhra to start up the process of removal of factory, she tells him to wait for some time. Anbu uses his brain and starts up the process, much to the annoyance of Rudhra. Soon, Kotraivel (Rajasimman) a member of Kodi's party finds out a camera, in which the video showing Rudhra killing Kodi is recorded and he threatens Rudhra to stop the factory issue. Rudhra uses the Inspector (Anil Murali) as a pawn, and lures him that she would promote him as D.S.P. if he would kill Kotraivel. They drive to the location where the member has called Rudhra. In between Anbu calls the inspector to inquire about Kodi's case and asks him where he is, to which he tells a wrong location to Anbu, but Anbu finds it out and follows him. When they meet the inspector holds him at gun-point and he gives the to Rudhra, but she already emptied the gun of inspector and gives the loaded gun to Kotraivel and he kills the inspector. That night police come to Anbu's house to inquire him about the inspector's death as he was the last one to call him. The police suspected that Anbu was pressuring the inspector. Rudhra arrives there and orders the police to leave. But Anbu questions Rudhra about Kodi which made her feel guilty and she leaves the place. Anbu tells Bhagat that he suspects Rudhra because when he followed the inspector he found his dead body and when he checked his phone there were many calls to Arivazhagan. But when he inquired Arivazhagan he told that it was him who sent goons to kill Rudhra and Kodi, but they did not kill Kodi and after that only Rudhra was present with Kodi. Rudhra begins to feel that Anbu will find out the truth and moreover, the documents related to the factory were being taken to the court by Anbu. In order to stop him, Rudhra kidnaps his mother and Bhagat and tells him to come to the factory. In the end, a fight between Anbu and Rudhra's goons along with Kotraivel and Marimuthu takes place which results in Anbu emerging victorious. When he is about to kill Rudhra his mother tells him to leave her, in order to remain lonely and unhappily for the rest of her life. Soon, Bhagat kills her saying she did not deserve to live and go away with Kodi.