Arivu is a writer for a press and the eldest son of a retired police head constable and his wife. He has a brother named Mathi (Mathiyazhagan), a first-year engineering student. Kumar is a family friend who blends into their circle, adding warmth and familiarity to their middle-class life.
The calm of their everyday life starts to fray when Mathi, pressured by his girlfriend to get a bike, persuades his family to buy him one. At first they hesitate, but eventually agree to get him a bike of his choice. Yet a delay in delivering the bike, coupled with the sight of a classmate Ganesh spending money casually, stirs Mathi’s curiosity about how someone like Ganesh earns what he spends.
Ganesh introduces Mathi to the brutal world of chain snatching and brings in Guna, who leads a gang of young thieves. Mathi steps into this dangerous underworld and begins to earn money through snatching, enjoying the trappings it buys him. He insists on doing these crimes on his own, without sharing a commission with Guna. The others initially hesitate, but they join in when two of the boys are caught by the police and Guna does not come to their aid, signaling Mathi’s growing audacity and willingness to go solo.
One night, Mathi returns home to retrieve a chain he has recently snatched, only to confront his mother’s presence among the items he keeps hidden from his parents. An argument erupts, and Mathi pushes his mother to death, an act that shatters the family’s world.
When Arivu and his father arrive home and discover their mother’s death, Arivu makes a vow to avenge the loss, with Kumar choosing to stand by him in this grim mission. During the ensuing police inquiry, Arivu and Kumar track down a house breaker and haul him to an unknown location, where they torture him and film the entire ordeal. Arivu then calls the police to hand over the house breaker and flees with a bag containing 23 kilograms of stolen gold chains to a black-market buyer. It is there that he unexpectedly finds his mother’s chain, a clue that leads him directly to the chain snatchers. He departs the scene, leaving no doubt that the gang will pay a heavy price, as he kills the men involved.
Meanwhile, Mathi uses a drug to inject Guna, pushing him toward insanity and a loss of control. Arivu heads to Guna’s place to uncover the snatchers’ next plan, and he and Kumar follow to confront the threat. A fierce confrontation unfolds, and the duo manages to kill several assailants. In a shocking twist, Mathi discards his helmet to reveal himself to be among the combatants, exposing himself to his brother and friend. The sight of Arivu and Kumar confirms the terrible truth for Mathi, who pleads for mercy, only to be met with Arivu’s quiet resolve to end the violence.
The morning after the brutal showdown, Arivu and Kumar reveal the truth to Arivu’s father and surrender to the police, a family torn apart by crime and driven toward a grim, irreversible finale.
