Vettaiyaadu Vilaiyaadu

Rani tells her father from a telephone booth that she will return to Madurai soon. An acquaintance approaches and she fails to come home. The next morning, Arokiya Raj finds Rani's index finger left at his door, triggering the investigation.

Raghavan discovers Rani's body within 12 hours, buried on the outskirts of Madurai. The autopsy reveals the killer slit her throat with a scalpel and bisected her body with an axe, signaling a medical background. With little solid evidence, the case remains open.

Six months later, Arokiya Raj and his wife Chithra relocate to New Jersey, seeking to escape the trauma of losing their daughter. The move marks a fresh start as they attempt to rebuild their lives in a new country.

Three months after moving, Raghavan learns that both Arokiya Raj and Chithra have been murdered in New York. He travels to the city to assist with the investigation, and on the flight he recalls his late wife Kayalvizhi, who was abducted and died.

Upon arrival, Raghavan stays at a Downtown Manhattan hotel and keeps his Chennai superiors updated on the investigation. He breaks into Aradhana's room to prevent her suicide by asphyxiation, saving her. Aradhana explains that her husband Arun is violent and seeking a divorce after cheating.

Raghavan and Lev Gorn uncover a link between Rani's murder and a two-year-old missing-person case involving Chandana, a 23-year-old Indian American whose finger was possibly found in her boyfriend's car. The two cases begin to converge into a single pattern.

Raghavan's instincts lead to Chandana's body in a restricted suburban area, found alongside three other American women killed in a similar pattern. The pattern narrows the pool of suspects to medical professionals with surgical training.

Flight records narrow suspects to two Indian doctors who studied at Brooklyn Medical University: Amudhan Sukumaran and Ilamaran Aanandhan, who are secretly involved in the killings. They murder their former professor Veronica, along with two NYPD officers in the same area where Raghavan had set them under surveillance.

Raghavan and Anderson visit the doctors' apartment, only to find it unoccupied. A break-in reveals photos of the victims and the murder weapons, confirming Amudhan and Ilamaran as the serial killers.

Before backup can arrive, Ilamaran arrives unannounced and kills Anderson, while Raghavan fights him and eventually knocks him unconscious. Amudhan stabs Raghavan with a scalpel to buy time.

To understand Amudhan's motive, Raghavan questions him about the killings. Amudhan explains they had a habit of killing from childhood, starting with pushing a classmate from a train at 13 and murdering their school teacher at 17; they stopped after entering MBBS at Rani's college. He claims their violent urges resurfaced when Rani provoked them, and Arokiya Raj assaulted the duo outside a theater.

Amudhan and Ilamaran's backstory reveals their pattern of killing since youth, their relocation to the United States for surgical training, and their eventual flight back to India to finish their targets before returning to the United States. They fled to Mumbai after burning their NYC apartment, were halted by Mumbai police, and eventually headed back to Chennai.

Raghavan survives with severe injuries and is cared for by Aradhana, strengthening their bond. Four weeks later, they return to Chennai together.

Aradhana reveals she has a daughter living with her parents in Chennai and is not ready for another relationship, choosing motherhood. Raghavan announces a statewide hunt for the killers, and the dean of the medical college revokes their degrees, marking the start of a violent manhunt.

Amudhan abducts Aradhana while Ilamaran attempts to infiltrate Raghavan's home. The police intervene, Ilamaran is captured, and the two killers are revealed to be bisexual in a hidden relationship. Raghavan defeats Amudhan and Ilamaran, avenging the fallen, revives Aradhana, and months later, he and Aradhana marry.