Madhan Kumar is an auditor by profession who lives in Chennai and also pursues music part-time at a local college. There, Mythili is a naive young woman who shares his interest in music, and the two gradually become friends after an unsettling vision Mythili has of him. Though she initially feels fear, she comes to see a gentler side of him, which deepens their bond against the city’s everyday bustle.
Yet behind this calm facade, he leads a brutal double life as a serial killer under the pseudonym “Manmadhan.” He targets and seduces seemingly immoral girls, then renders them unconscious with chloroform, before burning their bodies and preserving their ashes in labeled bottles. Each time he moves to strike, he experiences a nosebleed, a disturbing sign that marks the moment of his planned violence. His victims include a psychiatrist, a girl in a cafe, a train passenger, and several others, the pattern drawing increasing media attention.
As the city buzzes with the missing-girls case, Chennai’s new ACP, Deva, takes charge of the investigation. When Mythili sees Madhan Kumar riding with a girl on a bike, she is shaken; the next day the news reports a missing girl, and Mythili believes she has spotted the killer. She informs Deva, and Madhan Kumar is arrested in short order.
During interrogation, Madhan reveals a startling twist: his younger twin brother, Madhan Raj, is the real catalyst behind the murders. The narrative moves into a flashback that explains their shared past. The twins live with their maternal uncle, Puncture Pandiyan, in Madhampatty on the outskirts, while their parents are no longer present. Kumar is practical and brave, studying in Chennai to become an auditor, whereas Raj studies engineering in Coimbatore. Raj forms a close friendship with his hostel roommate Bobby Bobby and falls in love with Vaishnavi Vaishnavi, who returns his affection despite complications around her relationships.
Raj soon learns of Vaishnavi’s precarious situation: she is involved with Seenu, an arrangement that Raj’s confidant Ravi warns him about. Confronting Vaishnavi confirms her lack of true trust, and Raj discovers she and Seenu are not the innocent pair he believed. In a brutal turn, Raj kills Vaishnavi and Seenu after realizing their deceit, shocking Kumar and reshaping his worldview. Raj tells Kumar what he has done, and while he does not threaten him, Raj admits regret and, in a grave moment, dies by suicide soon afterward. This tragedy becomes the origin of Kumar’s own vow: to avenge Raj by targeting those who cheat in love—though he knows his path is morally complex.
To shield himself from discovery, Kumar adopts the Manmadhan identity and begins his reign of vigilant violence, letting Raj’s death stand in for his own guilt whenever he’s pressed. He battles with his conscience, knowing that his love for Mythili is genuine, yet he remains unable to express it openly, believing that justice for his brother’s pain justifies his brutal methods. Mythili, meanwhile, holds onto a fragile hope that Kumar might someday reveal his true feelings and choose a life beyond vengeance.
The film closes on a somber note: Manmadhan’s actions may evade immediate capture, but they are not beyond accountability—eventually, he must answer to the law and the moral reckoning that follows. Throughout, the story intertwines love, jealousy, betrayal, and the heavy cost of vengeance, leaving Mythili waiting and the audience to ponder whether innocence can survive in a world shadowed by crime and retribution.
