Vijay stars as Sivagiri, a bladesmith in a quiet village near Thirupaachi, who shares a warm bond with his beloved sister Mallika in the role of Karpagam. When a city man proposes to Karpagam, Giri agrees to the match and accompanies the newlyweds to Chennai. On that journey, he steps into a world of danger and responsibility, first by rescuing a court witness from Pattasu Balu, a fearsome gangster who dominates Central Chennai, portrayed by Pasupathy. Along the way, he also learns about Pan Parag Ravi, a North Chennai gangster who disrupts Karpagam’s husband’s canteen business, brought to life by Aryan.
During an altercation at a theatre, Kannappan is murdered by Saniyan Sagadai, a ruthless gangster who dominates South Chennai. Kannappan’s death marks a turning point, and Giri’s resolve hardens. After the funeral, he initially contemplates leaving his hometown, claiming a job at a cloth manufacturing company in Erode, but his mission to dismantle the city’s crime network keeps him grounded in Chennai. Giri reaches out to Sagadai with a chilling vow to kill him, and he also contacts Manoj K Jayan as ACP Rajguru, a connection that intensifies the clash between law enforcement and the underworld. His trusted ally, Yugendran as Inspector Veluchamy, at first resists Giri’s unorthodox methods, but changes course after Veluchamy’s son Arun is killed by Balu, pushing him to support the plan.
With Veluchamy providing a blueprint of the city’s crime network, Giri methodically marks the leading gangsters and begins cutting them down one by one, starting with Pattasu Balu—an act that signals a broader war against corruption. The North Chennai gangster Ravi, played by Aryan, escalates his own defiance by hiding in a politician’s house after being goaded by Giri; Ravi damages the property to provoke police attention, forcing security to be tightened around the politician. Through Veluchamy, Giri learns that Ravi is sheltering there, and he leads a rally of people who have lost money to a fraudulent financier hiding in the politician’s place. The crowd’s anger becomes a shield and weapon in Giri’s struggle, a turning point that allows him to penetrate deeper into Sagadai’s fortress.
As the police tighten the net, Raj orders his squad to strike, while Giri presses forward with a cunning, almost diplomatic strategy to inflame a war between the police and the gangsters. Disguising himself as a cop, he infiltrates Sagadai’s fort, aided by Veluchamy, who wounds himself in the process. A tense encounter follows as a thug is made to wear a police uniform and is killed, prompting Raj and his men to kill the others out of disbelief and anger, unaware of Giri’s true plan. In a climactic confrontation, Giri finally faces Sagadai and stabs him, throwing the crime lord to the ground just as the New Year arrives, delivering a stark act of vengeance for Kannappan’s death.
In the aftermath, Giri is reunited with his beloved Subha, and with Karpagam and her husband, closing a circle of loyalty, justice, and brotherhood that defines his relentless pursuit of peace in a city overrun by crime. Trisha Krishnan appears as Subha in the film’s emotional denouement, while Mallika returns as Karpagam, underscoring the personal stakes behind Giri’s formidable crusade.
