Prabhu Shankar is a happy-go-lucky middle-class man who spends time playing carrom in the streets with his friends Sathish and Kumar and others. He and his father keep falling into minor misunderstandings, and falls in love with a girl named Hema, who he meets at a bus stop. When he is caught in the act of stealing a pittance from his father for booze with his friends during one of his friends's sister's marriage, Prabhu questions his father's responsibility towards his upbringing, as a result, his father gives Prabhu some of his savings and tells him to do something with his life. Prabhu purchases a Bajaj Pulsar bike with the money. While his family initially berate him for buying the bike, he soon secures a job at a bank due to his bike, earning their respect. He forms an interminable attachment with his bike since it became his streak of luck, from getting a job to Hema eventually reciprocating his feelings. The bike eventually saves his life from a freak incident and gets lost during an outing with Hema, subjecting Prabhu to unfathomable anguish as he searches for his bike with his friends. When his family members asks him about his bike, he tells them that he had given it for dealer service.

Prabhu comes into conflict with the underworld when he witnesses a brutal murder planned by a gang in Kasimedu in North Chennai by a smuggling don named Selvam and his accomplices. Prabhu finds out that his bike was stolen by a petty bike thief who turns out to be in connection with Selvam's egoistical younger brother Ravi. Prabhu traces down the culprit and hands him over to the local police station. A formal complaint is lodged on the culprit on the same night. Later that night, Prabhu confesses to his family that his bike was stolen. His family is very upset, but Prabhu's father assures them that the bike will be found in no time, having developed a feeling of respect for Prabhu after he had become responsible by going for a job. The next morning, Ravi visits Prabhu's locality and threatens him to withdraw the complaint against the culprit. When Prabhu refuses, Ravi pushes Prabhu's father during the argument, which prompts Prabhu to hit Ravi. Ravi's accomplices arrive at the scene, and Prabhu manages to fight them all, leaving Ravi beaten and embarrassed among the public. Selvam returns home in bail after a murder charge. When he finds out what happened to Ravi, he gets furious and sends his henchmen to attack Prabhu without knowing the reason for his brother's embarrassment.

Meanwhile, Prabhu, along with Kumar, meets Selvam at his own residence in Kasimedu. Ravi is not home at that time. Prabhu tells the truth to Selvam, but the latter refuses to believe that Ravi and his men stole his bike. After hearing from his close ally Out, Selvam believes Prabhu, apologizing and promises Prabhu that he will do whatever he can to get his bike back, but it was too late for Prabhu's father, who receives the attack from Ravi's men. He was admitted in a hospital, and Prabhu breaks down after knowing that his father may never walk again after his right leg is paralysed by the attack. Selvam, Ravi, and their men visit Prabhu to condole and apologize for what happened this time. Prabhu turns down the apology, and again, an immediate fight is about to break between Prabhu and Ravi before Selvam separates them both, blaming Ravi for the ordeal caused. The attack on his father makes Prabhu realize how much he loves his father and swears to protect his family at any cost. Although he wants to stay away, Prabhu invariably gets dragged into rubbing shoulders, caused by Ravi's antics, who now targets his family to seek revenge. Prabhu's bike is caught by the NCB and they nab him, suspecting him of drug smuggling in his bike.

They release him after Prabhu tells them that his bike was stolen and shows them his FIR copy, but he does not tell them about Ravi or Selvam. Now, Prabhu learns that his bike was stolen by Selvam's men to escape from a murder scene, but it was Ravi who smuggled drugs in his bike's petrol tank. Prabhu loses his job as an employee in his workplace since his bike was a source of transportation, and as he was kept at police custody for one night. Prabhu also gets despair from Hema's father (Boys Rajan) for being involved unwillingly with Selvam's men. Meanwhile, Ravi makes one more attempt at Prabhu's life, but he is snubbed again by Prabhu. Selvam becomes unhappy about this and warns him to quit smuggling if he ever gets in Prabhu's business anymore. Ravi accuses Selvam of being a non-caring brother, and Out intervenes and warns Ravi to mind his language. Surprisingly, Selvam himself comes in support of his brother to lash out at Out. Out separates briefly from Selvam after this conflict. The next day, Selvam and Ravi get attacked by unknown gangsters when they are traveling in their car outside the city. Selvam asks his brother to stay inside the car and handles the killers on his own. He gets brutally injured only to find out that he has been stabbed by his own brother Ravi. The attack was arranged by Ravi himself to kill Selvam. Ravi delivers the killer blow before telling that Selvam is too complacent of Prabhu and he is going to kill him, after which Selvam dies.

Ravi creates a scene among Selvam's family and henchmen. Out, who is not aware of the mastermind behind the assault on Selvam. Out gets furious and vows to kill every enemy of his mentor Selvam, including Prabhu. Prabhu eventually gets his bike back, but is disheartened when he finds it vandalized, so he takes it to the service centre for restoration. While there, he learns that Ravi is after him and his family. He first goes to save Hema. After securing her, he goes to save his family. He thinks that the only way to stop this is to confront Ravi himself. He takes down all the men sent by Ravi, who comes in his way. Meanwhile, Prabhu's family are chased down in Kumar's auto rickshaw by Ravi's men. Prabhu finds Ravi hiding in an ice factory and engages in a fight with him. Prabhu overpowers Ravi during the fight; the latter tries to escape from him but finds the shutter of the ice factory blocked. Prabhu manages to subdue Ravi under the knife, threatening him to ask his men to leave Prabhu's family, which he does, and his men spare Prabhu's family and Kumar. When Prabhu is about to leave, Ravi provokes him to continue the fight until death. Prabhu manages to dodge Ravi's swing of his knife and gets a steel rod to fatally knock him down. Out arrives at the scene after having learnt that it was Ravi who orchestrated Selvam's death, hence he was the one who had blocked the shutter of the ice factory as Ravi tried to flee. Out smiles at Prabhu and lets him go while he stares down at Ravi's corpse, satisfied that Prabhu had done his job for him, avenging Selvam's death and remembering his words of Prabhu: "He is fearless and should be spared." Prabhu leaves the scene in his beloved Pulsar bike.