Viduthalai: Part I

In 1987, a catastrophic train derailment strikes a rural Tamil Nadu village, leaving many injured or dead. Rescue teams rush to evacuate victims and secure the wreckage as investigators begin probing the incident. Officials indict the extremist group Makkal Padai as the alleged protestors behind the derailment and announce Operation Ghosthunt to capture their elusive leader, Vaathiyar Perumal.

Kumaresan is a newly recruited constable who joins the police batch E-Company as a driver. He quickly discovers the muddled alliances, backroom deals, and the harsh realities of police life. He learns that following orders can conflict with his urge to help the locals, marking the start of a challenging career.

During his early days, Kumaresan meets Tamilarasi 'Pappa' and is drawn to her. Pappa is the granddaughter of a woman Kumaresan once rescued after a bear attack and admitted to hospital. Their budding romance grows amid the tension between duty and personal loyalties.

A brutal incident orchestrated by E-Company's Officer-in-charge Ragavendar triggers a government response. In consequence, the government assigns DSP Sunil Menon to lead Operation Ghosthunt and target Perumal. The shift brings higher stakes and a new leadership approach to the operation.

To isolate Perumal, the police decide to turn the hill villagers against him. Sunil interrogates a villager and sketches Perumal's face, tightening the net. Meanwhile, Kumaresan realizes the people he helped were Perumal and his men, and he informs Head Constable Chandran, unaware that Chandran is a Makkal Padai mole.

Chandran, secretly a member of Makkal Padai and Perumal's mole, tips Perumal off about Kumaresan's actions. This leak escalates the risk for Kumaresan as he navigates the investigation. The betrayal deepens the tension between the police battalion and Perumal's group.

Makkal Padai makes an assassination attempt on Kumaresan; the attack is made to look like an assault on Sunil. Kumaresan escapes unscathed and reaches the camp with Sunil's timely help, keeping the operation alive. The incident heightens the sense of danger around Perumal and his supporters.

Pappa reveals that Perumal targets officers who abuse innocents, and that some officers were involved in her father's death, triggering her mother's mental breakdown. The revelations deepen Kumaresan's understanding of police brutality and the locals' suffering. This information fuels his conflict between duty and conscience.

During hilltop construction, Makkal Padai attacks the inauguration ceremony, provoking a violent clash. An accidental bomb blast kills four officers, intensifying government anger. The attack triggers a brutal crackdown by Sunil against villagers.

Enraged by the violence, Sunil orders arrest of villagers suspected of aiding Makkal Padai. Villagers are dragged away for interrogation, and Pappa's grandmother is killed during torture. The crackdown exposes the heavy price paid by innocents in the pursuit of Perumal.

Pappa is arrested and tortured along with other villagers. Kumaresan is left desperate to find her among the detainees. The police believe one detainee is Perumal's close relative, adding to the tension and stakes.

Kumaresan seeks out Sunil and shares information about Perumal's hideout. Sunil assigns him, along with other officers, to arrest Perumal. The pursuit tightens as Perumal's whereabouts remain hidden.

After a massive shootout, Kumaresan arrests Perumal in custody. Pappa tries to draw attention to save others and is taken away. Perumal is interrogated by the police, while Ragavendar suspends Kumaresan for not filing an act-of-subordination memo and claims credit for the arrest.

In the mid-credits sequence, a photographer secretly records police atrocities against women in the camp. Perumal is insulted by Sunil during interrogation but later escapes to meet Kumaresan in the forest. He reveals crucial information about the train attack and urges the authorities to seek the truth.