Kaali is an impulsive and short-tempered working-class man who works in an IT company and enjoys playing football during his free time. His best friend is Anbu, a young political aspirant. They live in the dilapidated flats of a housing board in Vyasarpadi, North Chennai, along with their friends.

Meanwhile, in a long-standing bloody feud, two factions of a political party have been laying claim to a wall on which they can paint the portraits of their respective political leaders. Anbu, under the local leader of one of the parties, Maari, is determined to claim that wall for their own party. Kannan, the chief's party, along with his son Perumal are hell-bent on making sure that their opponents's efforts go in vain. The painting of Kannan's father Krishnappan's face has been on the wall for two decades, since the start of the feud.

The two parties and their supporters get into frequent clashes and scrapes. In the meantime, Kaali falls in love with a politician's daughter Kalaiarasi, but she remains cold with him. In a spur of motivation due to the upcoming elections, Anbu reserves the wall for their party. Although the wall is in their area and technically theirs, the opposition asks Anbu to give it up as the portrait of their patriarch had been there for quite some time. Moreover, since three deaths had previously taken place in connection to the wall, along with the deaths of members from both parties, people have started to consider the wall as a bad omens.

When Anbu declines, a goon of Kannan's starts insulting Anbu, Kaali attacks him, leading to Kannan seeing Anbu as the reason for Maari's resurgence. Kannan's henchmen plan to kill Anbu and Kaali. Kalaiarasi professes her love to Kaali. When the henchmen try to kill Kaali and Anbu, they escape and hide behind a van. They see Perumal, who does not notice them, talking on a phone, giving orders to kill Anbu at any cost. Kaali then kills Perumal with a straight hit to head using a crowbar. Anbu and Kaali are told by Maari to surrender at Kanchipuram district court to avoid being killed by the henchmen.

However, the FIR contains Anbu's name. Anbu takes responsibility of the murder, despite Kaali being against it, and hopes to be released soon, Kannan's henchmen hack Anbu to death and seriously wound Kaali outside the court. Kaali slides into depression by guilt and swears revenge, attempting to kill Kannan. Afterwards, he is berated for his short temper by his parents and Maari, who want him to get his life back together. Maari assures Kaali, Anbu's death will be avenged. Kalairasi begins to comfort Kaali, where they spend time together and get married.

One day, Kaali and Kalaiarasi arrive at a restaurant, where he notices one of Maari's henchmen sitting at the next table. When he goes up to the henchman for a chat, the latter runs away in fear. After Kaali catches him, he learns that Maari had joined hands with the opposing party to become MLA of RK Nagar and was the brain behind Anbu's assassination. Though reluctant, Kalaiarasi lets Kaali to pursue his vengeance.

At a local meeting where Maari is being felicitated, Kaali spills the beans and the locals chase Maari out. Kaali splashes paint on the wall, thus ruining the portrait. Soon, everyone follows suit. Maari plots to kill Kaali, but is betrayed by the touted successor of the opposing party. In a final showdown, Kaali subdues the henchmen sent to kill him and grievously injures Maari, who is soon killed. Kaali and Kalaiarasi start teaching about in the building whose wall was the cause of this bloody feud. The wall now has a theme of children's education painted on it. However, Kannan still wants to have his father's portrait on the wall.