Manmadhan

Madhan Kumar works as an auditor in Chennai and also pursues music as a part-time student. Mythili, a naive woman who also studies music at the same college, becomes his friend after an initial uneasy encounter. Their friendship grows against the backdrop of the bustling city and shared musical interests.

Unknown to others, Madhan Kumar leads a double life as a serial killer named Manmadhan. He hunts seemingly immoral girls, seduces them, and uses chloroform to render them unconscious. After killing them, he burns the bodies and keeps ashes in bottles labeled with their names.

Before every planned murder, he experiences a nosebleed, a grim sign that something sinister is about to happen. This physical cue accompanies his cold, calculated method of ending the lives of his victims. The killings spread a sense of fear across the city.

The string of missing girls attracts heavy media attention and public concern. Chennai's new ACP Deva is assigned to track down the killer and bring him to justice. The investigationtightens as the city awaits a breakthrough.

Mythili spots Madhan riding a bike with another girl, fueling her suspicions. The next day, a girl goes missing, and Mythili informs ACP Deva about Madhan's whereabouts. This information triggers a chain of events that leads to Madhan's arrest.

During interrogation, Madhan reveals that his younger twin brother Madhan Raj is responsible for the murders. The confession shifts the narrative into a flashback that delves into their past. The revelation reframes the killer's identity from Madhan to his brother.

Madhan Kumar and Madhan Raj grow up with their maternal uncle Puncture Pandiyan in Madhampatty, on the outskirts of Coimbatore district, after their parents die years ago. Kumar is brave, intelligent, and practical, while Raj is innocent and sentimental. Kumar moves to Chennai to study for auditorship, while Raj stays in Coimbatore to pursue engineering.

Raj becomes close with his hostel roommate Bobby and falls for classmate Vaishnavi, who reciprocates his feelings. However, Ravi hints that Vaishnavi is involved with Seenu, a relative studying in the same college. Raj confronts Vaishnavi and begins to doubt the sincerity of her love.

Raj visits Vaishnavi's house to apologise after a confrontation, only to witness her having an illicit affair with Seenu. He overhears Vaishnavi plotting to use Seenu for her own ends, which shatters his trust. Enraged by betrayal, Raj murders Vaishnavi and Seenu.

Raj boasts to Kumar about his killings and declares he will continue to target women who cheat in love, taking on the persona of Manmadhan. He threatens to kill Kumar if he informs others and hints that his true identity will stay hidden for now. The seeds of the masked killer myth are sown.

In the present, the police close in on Raj's victims as more evidence surfaces. Kumar, aided by Pandiyan, is released from the case and Mythili apologizes to him, even proposing love. Kumar rejects her, explaining that he loves her only as a friend and cannot return her feelings.

In another flashback, Raj meets Kumar after his killings and expresses regret for what he did, claiming he acted out of impulse. He eventually commits suicide, leaving Kumar to confront the consequences. This tragedy sharpens Kumar's resolve to punish those who cheat in love under the Manmadhan identity.

Kumar adopts the Manmadhan identity to avenge Raj's death by targeting girls who cheat in love. The murder spree resumes under the alias, and the nosebleed signal of guilt continues to haunt him during each kill. He also uses the Raj cover as a shield to dodge suspicion.

Kumar maintains that Raj's death remains hidden, allowing him to sustain the killings without exposing his own identity. He crafts a narrative that the killer is a separate figure, effectively keeping Raj's memory buried as part of his deception. This keeps his plan of vengeance intact.

The film closes with Kumar admitting his love for Mythili, yet choosing to prioritize his brother's death over romance. He asserts that only God can judge his actions, and the message implies that Manmadhan may have escaped the police for now but will one day answer to the law. Mythili remains hopeful that Kumar might someday reveal his true feelings.