Vikram is a brave and honest police inspector who is decisive about right and wrong. Vedha is a criminal who understands the grey shades between good and evil. Vikram leads an encounter unit formed to eliminate Vedha. In one encounter, the squad kills some of Vedha’s henchmen, framing the death of a criminal killed by Vikram to avoid further inquiry. When Santhanam, one of the youngest members in the unit, is nervous about this, Vikram calms him by saying that he sleeps peacefully, knowing that the men he shot were criminals. As the unit plans another encounter, Vedha enters the police station and surrenders. When Vikram interrogates Vedha, he offers to tell him a story.
The story relates to how Vedha became a gangster and drug smuggler. Vedha warns his younger brother Vignesh, called Pulli due to his arithmetic skills, to stay away from crime, but Pulli is forced by a rival gangster, Ravi, to carry drugs. When Pulli is caught by the police, he confesses, and Ravi is arrested. On his boss Sangu’s orders, Ravi assaults Pulli, leaving a permanent mark on his hand. Vedha asks Vikram if he should kill Ravi or Sangu. Vikram replies that Ravi was an instrument; Sangu was the real culprit. Vedha says the answer is correct, implying that he killed Sangu. Vedha’s lawyer, who turns out to be Vikram’s wife Priya, intervenes and bails him out.
Vikram realises that the unarmed person he shot was Pulli, based on the mark in his hand. Worried that Vedha might try to kill his colleague and best friend Simon, Vikram rushes to save him. He finds him and Chandra, Pulli’s girlfriend, shot dead. Surendhar, the superintendent of police, dismisses it as a failed encounter. Priya refuses to divulge Vedha’s whereabouts to Vikram, testing their marriage. Angered by this, Vikram raids Vedha’s tenements and manages to capture him. Vedha requests Vikram to listen to another story.
The second story starts with Pulli, now an adult, offering to launder Vedha’s income investing it in shares. Vedha’s boss Cheta invests five million rupees in this venture. However, Chandra is supposedly kidnapped, and the money is missing. Chandra returns and reveals that she stole the money to start a new life but came back because she loves Pulli. Vedha returns the money to Cheta, who orders him to kill Chandra. Vedha asks Vikram if he should respect Cheta and carry out the order or disobey him and support Pulli, resulting in a gang war. Vikram replies that he should support Pulli, to which Vedha agrees. Realising that Pulli’s innocence causes Vikram to stumble momentarily. Vedha attacks and subdues Vikram, telling him to investigate Simon and Pulli’s deaths.