The film begins with a scene from a police station where Sasi, the police officer in charge, orders that the documented criminal cases in the form of manuscripts be converted into digital format. During this process he comes across a really spine chilling dacoity murder case from several years ago. After reading the case history, he calls up the police officer who had taken charge of the case, Theeran Thirumaran (Karthi).
The story shifts to the year 1995, where Theeran is in his police training college undergoing training to be posted as DSP from TNPSC (Tamil Nadu Public Service Commission) exams. He tops the training period. Simultaneously, in a house along the highway of Tamil Nadu, a group of dacoits wreck the house by barging in killing all the people inside gruesomely and taking the belongings.
Meanwhile, Theeran returns to his hometown of Tanjavur, falls in love with his new neighbor Priya (Rakul Preet Singh), and marries her. Later, Theeran becomes known in the police department for his ways of handling various cases and he is later moved to Ponneri after a dacoital attack. Police Inspector Satya (Bose Venkat) and Theeran both handle the case, but lead nowhere with the case. Therefore, in 2003, Theeran, Sathya, and a group of other police officers go around India to see if they are able to identify the fingerprints of the dacoits. During this process Theeran learns that these dacoits are actually tribe members of the left over cultural groups after the Indian Independence. They are eventually stopped by the carelessness of their superior officers and the case is put on hold.
Later in 2003 the dacoits raid the house of the ruling party's MLA and kill him. The government is under heavy pressure from the public, and the Home Minister gives Theeran all powers and a full team to nab the dacoits. A year later, they find one fingerprint match in Uttar Pradesh prison and go to a lorry station to capture the dacoit. Learning that the lorry has left and it is heading to Ponneri, Theeran and the other officers rush to stop them. The dacoits raid Sathya's house and kill his wife (Sonia), and also injure Priya and put her in a coma.
Angered by this incident, Theeran, with the help of higher officials, puts together a team to capture the gang of dacoits lead by Oma (Abhimanyu Singh). They camp in Rajasthan with the help of a local police officer. They come to know that the gang members except Oma are in their village so they visit the village only to be sent out by the villagers. While the case is going on, Theeran learns that Priya died. This fuels his anger, which makes him even more motivated to find Oma. The team learns that there is a way to bring Oma out from his village. So he captures the organizer of the gang and one of the gang members and puts them in police custody. Infuriated Oma vows to kill Theeran and his team. Theeran gets information that Oma will be on a train which is infiltrated by the team, but Oma escapes to a nearby village. Theeran and his team walk to the village and reside there for the night. Oma's gang infiltrates the village, destroying it and killing Theeran's teammates. Finally, Theeran captures Oma, brings him to Tamil Nadu, and gets him a death sentence.
Now in 2017, it is revealed that Theeran has a boring useless post in the Traffic Vigilance Department because he is straightforward and lives alone. Theeran is visited by Sathya, Sathya's daughter, and Sasi. Sasi salutes him. The movie ends with a note conveying "The film is dedicated to all the people in the police department who fought and arrested those dacoits, and we thank them for their bravery and courage. The officers involved in this case were not recognized by the government by providing any honorary awards, neither were they promoted to higher posts".