Arjun is an ACP known for his unorthodox approach to apprehending suspects, often preferring lethal confrontations over standard arrest protocols. He harbors affection for Priya Nayanthara, the sister of his colleague and friend, Andrew [Narain], but hesitates to commit to marriage due to the enemies he has amassed during his aggressive law enforcement career.
The city is gripped by fear as a psychopathic serial killer, nicknamed the Smile-Killer for leaving distinctive smiley-face notes near the crime scenes, abducting and gruesomely murdering young girls. Arjun and Andrew are assigned to this harrowing case. Tragically, Andrew loses his life while confronting the killer, who is later identified as Brahma [Rahul Bose]. Haunted by the trauma of this investigation, Arjun resigns from the police force. Together with Priya, he opens a cafe, seeking a tranquil existence.
A year later, panic resurfaces when reports suggest that Brahma has escaped from prison. Subsequently, Shanmugam, the doctor responsible for Brahma's care while incarcerated, is found dead. Shanmugam's daughter Swetha also falls victim to the same gruesome fate as Brahma's prior victims, bearing the killer's signature. Arjun is sent a death threat letter, seemingly from Brahma. The Smile-Killer's spree intensifies, with increasingly brutal acts and the disturbing practice of sending video footage of the victims' torment and murder to their families and the media. The grim videos drive some family members of the victims to commit suicide.
The disappearance of Shalu, the only survivor of a previous encounter with Brahma, draws the attention of the police and Arjun. There is a belief that Brahma has abducted her once again to complete his unfinished task. Investigations reveal that Brahma may not intend to kill Shalu because he sees her as a willing participant, given her nymphomaniac tendencies. In a previous abduction, Shalu's response to Brahma's torture was arousal rather than fear, which diverged from Brahma's typical satisfaction derived from his victims' screams of panic. Arjun eventually locates the site where Shalu is held captive, the same place where Brahma was previously apprehended. A confrontation ensues, during which Arjun questions Brahma's role and discovers that someone else has been using Brahma's name for the most recent murders, but Brahma refuses to reveal the other person's identity. The police arrive and fatally shoot Brahma.
The Smile-Killer's reign of terror continues, raising suspicions that another individual is impersonating Brahma. After a thorough investigation, Arjun believes that Babu [Vinoth Kishan], an assistant to Church Father Sebastian and a previous suspect, is the copycat killer. However, evidence implicates Arjun when it is revealed that the video of Shalu's captivity was sent from his location. In an attempt to apprehend Babu, Arjun uses his characteristic aggressive methods. The police intervenes to save Babu, and in the heated exchange, Arjun confesses to kidnapping Shalu and sending the video to a TV channel. He insists that it was a play to trap Brahma as he knew that Brahma considered Shalu a partner rather than a victim. Meanwhile, Babu goes to the media regarding his mistreatment at the hands of Arjun and the police force, leading to the public sentiment leaning in his favor.
Later that evening, Arjun uncovers compelling evidence at Babu's store that links him to the crimes. En route to Babu's arrest, he receives a phone call from Andrew's widow Jasmine Vijayalakshmi Agathiyan who reveals that Babu has abducted her daughter Sophie. Babu promises to disclose Sophie's location only if Arjun complies with his demands. Arjun agrees and embarks on a journey to meet Babu, but a tragic turn of events occurs when Jasmine attempts to take her own life, seemingly as part of Babu's demands. Ultimately, a hostage exchange takes place with Priya joining the scene, per Babu's request for her in exchange for Sophie. In the process, Arjun intervenes, incapacitating Babu and saving both Priya and Sophie.
The police force fakes Babu’s death due to the public sentiment regarding his innocence and holds him captive in secret. The movie ends with them leaving the room so that Babu can be dealt with by Arjun.
