Whistle

Swetha, a college student, is found dead in her car on a highway, signaling the start of the mystery. No one who knew her seems to have heard from her since the day of the incident. She belonged to a circle of friends at the college—Jeeva, Anjali, Bharath, Vinod, Meera, Sharmi, and Maya—whose fates quickly become intertwined with the killer’s identity.

The college is famed for rumors of the serial killer Naga, though many dismiss it as a hoax. Behind the college sits an old laboratory where a devastating fire in 1987 killed all the occupants. A temple supposedly buried Naga, and the college was later built after demolishing the temple, further feeding the myth.

Maya and Anjali sneak into the abandoned lab behind the college at night and encounter Vinod, who is only pretending to be dangerous. The prank quickly sets a tense mood as the ghostly setting fuels the fear surrounding Naga. The incident also foreshadows how appearances can deceive in this mystery.

Professor Pannerselvam delivers a lecture about Nagammal, the origins of Naga, and the brutal fate of those who crossed her. He explains how a temple and a village curse tied to the myth fuel rumors of murder around the campus. His belief in the legend contrasts with the students' skepticism.

Swetha's death is initially treated as an accident, raising doubts among those who knew her driving skill. Inspector Syed grows suspicious that a rival business interest could be involved. The case becomes the first sign that the rumor of Naga might be more than superstition.

Vinod corners Anjali in the abandoned woods and makes a failed advance, revealing the dangerous edge of his bravado. Soon after, he is found dead—hung in a manner that suggests a killer wearing a Naga mask. Anjali is left terrified, realizing the killer could be closer than anyone imagined.

Anjali grows suspicious and searches the campus library for clues. She discovers a book on Naga whose illustrations eerily match the manner of Vinod's death. Sharmi notes that Vinod was the last to borrow the volume, hinting at a planned trap rather than a real haunting.

Meera is attacked in her room by the Naga and is found dead, her drug-induced despair underscoring the darkness of the campus murders. Anjali realizes the killings are not random and are connected to the legends they discussed. The death shocks the group and intensifies the investigation.

Jeeva, Anjali, and Maya break into Professor Panner's room to investigate and hide in a secret room behind a shelf. They find a ritualistic Naga outfit—mask with snake embroidery, a black cloak, and an axe—that links the professor to the killings. Anjali notes the axe resembles the weapon used to kill Meera, deepening the suspicion around Panner.

Jeeva publicly shames Panner in the college magazine, prompting the principal to suspend him for a week. Anjali reveals she has a police record from school, a detail that ignites distrust within the group. The tension between students and faculty grows as suspicions turn inward.

Maya confides that the recent murders align with the illustrations in the old Naga book, suggesting a deliberate pattern. The group considers where the next murder could occur, and a figure resembling Naga by the swimming pool unsettles Maya and Anjali. The discovery links to past school-day secrets rather than random chance.

Flashbacks reveal that during school, the six friends ragged a junior named Saravathy on Whistle Day, leading to her suicide and leaving dark memories behind. Jeeva holds Saravathy's photo, foreshadowing how guilt and secrets can drive current violence. The past explains the motive behind the killings.

Barath vanishes during the college annual day and is found dead soon after, followed by Professor Panner’s murder. Maya and Anjali visit Jeeva's home and discover Panner’s corpse, prompting a frantic escape as Inspector Syed arrives. The trio soon realizes the danger is personal and not a rumor.

Jeeva confronts the group and reveals that there are two Nagas, Maya and Baji, who have been murdering in tandem. Maya explains Saravathy is her sister and that Baji served as their ally and caretaker; together they planned revenge and killed Panner to cover their tracks. In the climax, they attempt to bury Anjali alive, but Jeeva interrupts, Baji is killed, and Syed shoots Maya.

Years later, a new batch of students studies the Naga legend, with some denying its truth. Maya returns to the scene and admits that she generally believes in Naga, implying the story’s cycle will continue with new believers and skeptics. The legend endures, haunting the campus even as the bodies have long cooled.