The film begins with a serial killer setting ablaze a lifeless body on a desolate street. As the murders continue, the death toll reaches 6, and
ACP Ranjith Kumar is initially assigned to the case. However, after Ranjith gets into a coma due to a road accident, the case is handed over to ACP Aravindan, a brilliant and resolute officer, who had recently apprehended a finance robbery team led by Dheeran. Aravindan, along with
Sub-inspector Manoharan, a cardiac patient and a single father, starts investigating the serial killings. Meanwhile, Sanjana, who had mistakenly met Aravindan thinking he was her prospective groom, falls in love with him, but Aravindan doesn't reciprocate her feelings. Aravindan discovers a crucial piece of evidence, an ankle-surgery plate in one of the victims, which helps them shortlist 7 individuals based on age. One of the suspects is Sudhakar, who has a history of ankle surgery. Next, Aravindan meets Meera, the twin sister of one of the victims. Meera's connection to Twin Birds school, where a similar photograph is found in Sudhakar's house, hints at a deeper connection between the suspects and victims. During the interrogation, Sudhakar and Meera reveal a shocking truth: they're Surendhar and Tara, who impersonated their identical twins, Sudhakar and Meera, respectively. They explain that their twins went missing, and they received a video call from a masked assailant who kidnapped them and forced them to kill a person with a covered face. The twins were threatened that if they refused to kill, their respective siblings would be killed. To save their siblings, they committed the murders. However, they later discovered that they had unknowingly killed their own twins, whose faces were covered during the act. To evade police investigation, Surendhar and Tara assumed the identities of Sudhakar and Meera. Aravindan learns that the only connection between the twins is their school, Twin Birds Matriculation School. Surendhar and Tara suspect that their classmate, Benjamin, might be behind the sinister plot, forcing them to commit
fratricide. Aravindan decides to meet the school's correspondent, Shanthi, to uncover more information about the twins' past and potential connections to Benjamin. Shanthi and her husband Ravi adopted twin brothers, Benjamin and Francis, impressed by Benjamin's chess talent. The brothers were raised at their school, Twin Birds Matriculation School. Benjamin turns into a chess prodigy, bringing laurels to school, and Francis becomes a topper in studies, which envies their fellow students. Tragedy struck when Francis, who suffered from
nyctophobia, was mocked by his classmates and locked in a dark chemistry lab. This led to a fatal epileptic seizure. Benjamin, who was in the physics lab, couldn't rescue his brother. After Francis's death, Benjamin was cared for by Mother Helen and later adopted by an unknown family. Shanthi reveals that her husband kept Francis's death a secret to protect the school's reputation. However, the school was later destroyed in a fire, and Ravi died due to excessive drinking. Aravindan obtains the records of the classmates and discovers that Benjamin is targeting twins on their birthdays. The remaining twins, Sanjana and Anjana, and Dheeran and Dheeraj are potential targets. Aravindan takes immediate action to safeguard Sanjana and Anjana, especially since Dheeran and Dheeraj are unreachable. Sanjana, who has feelings for Aravindan, is unaware of the danger looming over her. The investigation takes a turn when Aravindan discovers the charred corpse of Dheeran. Meanwhile, Ranjith Kumar, who was initially investigating the case, reveals that his
coma was due to a preplanned murder attempt. He also reveals that the killer rescued him and placed him near the hospital. Aravindan learns from Shanthi that Benjamin visits Francis's cemetery every year on the latter's death anniversary. Aravindan rushes to the cemetery and discovers that Manohar is Benjamin in disguise. After an intense chase, Aravindan loses Benjamin and rushes to protect Anjana and Sanjana, but gets beaten by Manohar. When Aravindan wakes up, he finds that Benjamin has kidnapped Anjana. A fight ensues, and Aravindan hands over his gun to Sanjana to stop Benjamin from killing Anjana. However, Sanjana ends up shooting her twin sister, Anjana, believing Aravindan's instructions. The truth is revealed that Aravindan is the real Benjamin, who has been planning his revenge against his classmates responsible for Francis's death. Benjamin surrenders to Ranjith Kumar, who recognizes him as the killer using his lighter box. Benjamin confesses to Ranjith Kumar that he had pursued an
IPS career to avenge his brother Francis's death by killing the 10 twins who were responsible. He also reveals that he planned the road accident to distract Ranjith and to take over the case, and had also threatened to kill Manohar's son and made him act as Benjamin to protect himself while killing Anjana. Benjamin, aka Aravindan, is sentenced to death for his crimes. Soon, Ranjith is shocked to learn that Benjamin had cleverly burnt an unknown corpse and claimed it as Dheeran, and also voluntarily revealed him as the killer to Ranjith, so that he gets closer to Dheeran, whom he had arrested in the finance robbery case without knowing Dheeran's true identity. Before Ranjith Kumar and Manohar can safeguard Dheeran, Benjamin kills him in prison, fulfilling his revenge. In a shocking twist, Benjamin takes brain-dead pills and dies, but not before donating his heart to Manohar. Manohar fulfills Benjamin's last wish by burying him near Francis's grave. ==Cast==