| Director | A. R. Murugadoss |
|---|---|
| Budget | ₹7 crore |
| Box office | ₹50 crore |
Chitra is a medical student, who along with her friends is working on a project about the human brain. Chitra wants to investigate the curious case of Sanjay Ramaswamy, a notable Chennai-based rich businessman who is reported to have anterograde amnesia. Her professor Ravindran denies access to Sanjay's records as it is currently under criminal investigation. Overcome with curiosity, Chitra proceeds to investigate the matter herself in secret.
Sanjay loses his memory every 15 minutes and uses a system of photographs, notes, and tattoos to recover his memory after each cycle. It is revealed that Sanjay is ultimately out to avenge the death of his lover Kalpana and that he is systematically killing the people responsible. His main target is Lakshman, the head of a Kolkata-based human trafficking network and a notable socialite in Chennai. Inspector Ravi is on the case of the serial murders. He tracks Sanjay at his flat and knocks him unconscious. Ravi finds two diaries titled 2002 and 2003 where Sanjay has chronicled the events of his life.
In 2002, Sanjay, the owner of the AirVoice mobile telephone company, meets Kalpana, a struggling advertisement model, and secretly develops romantic feelings for her while introducing himself as "Manohar". Eventually, they spend time together and gradually develop a liking for each other. The diary ends with Sanjay proposing to Kalpana and promising himself that he will reveal himself as Sanjay Ramaswamy if she accepts.
Before Ravi can read the 2003 diary, Sanjay regains consciousness, attacks and ties him up. He tracks down Lakshman to a college function where the latter is the guest of honor. Sanjay takes pictures of Lakshman and decides to kill him. However, he mistakenly attacks and kills one of Lakshman's goons in the parking lot. Lakshman is perplexed and fails to recollect the incident. He decides to find and kill his enemies one by one, but Sanjay is not among them. In the meantime, Chitra visits Sanjay's flat and finds Ravi, beaten and bound. Chitra finds the two diaries and frees Ravi. She also finds that Lakshman is Sanjay's target. Ravi tells her that Sanjay is a known serial killer. Sanjay arrives suddenly; he remembers neither of them and chases them out. Ravi is eventually hit and killed by a bus, while Chitra barely escapes, going into a phone booth.
Believing Lakshman is in danger, Chitra informs him that Sanjay is after him. Sanjay discovers that Chitra had warned Lakshman and goes to her dormitory to kill her, but Chitra calls the police and Sanjay is arrested. Lakshman discovers about Sanjay through a police inquiry and arrives at Sanjay's flat, destroying all the photographs, notes and scratching off Sanjay's tattoos. Chitra reads the 2003 diary, which states that Kalpana accepted the proposal, but on the condition that she marry only after she completes her past commitment. The diary ends abruptly as Sanjay left for a business trip. Chitra investigates further and discovers that Kalpana was traveling to Mumbai for a modeling assignment by train when she rescued 25 innocent young Tamil girls being trafficked to Mumbai and Kolkata. Lakshman, the ringleader of the racket, killed two girls who recognized him and went in search of Kalpana. His goons broke into her apartment and tried to kill her, only to be trashed off by Sanjay, but Lakshman attacked Sanjay and kills Kalpana with an iron rod.
Now aware of the truth, Chitra finds Sanjay in the hospital and tells him everything. Sanjay tells her to lead him to Lakshman. Meanwhile, Lakshman's twin brother Ram arrives from Kolkata to help him pursue Sanjay. Arriving at Lakshman's factory in downtown Chennai, Sanjay sees Lakshman leaving in a car and follows him, but Chitra calls him and tells that he is here thinking that Ram is Lakshman, which everyone hears. Ram and his men try to kill her but she escapes to her dormitory. Ram and his henchmen arrive along with Lakshman and ask her to bring Sanjay, threatening to kill her friends otherwise. She goes to find Sanjay, along with their henchmen and finally finds him. Sanjay confronts and disables all of Lakshman's henchmen and goes to the dormitory to kill Lakshman. Sanjay fights off Lakshman and Ram but gets badly beaten and injured by them. But when he sees Kalpana's presence and recollects how Lakshman killed her, he overpowers and kills the brothers.
With his vengeance fulfilled, Sanjay leaves with Chitra, where he stops at a crossing to let young children cross the road. A young girl smiles at him and he returns the smile. Sanjay feels a presence of Kalpana in the child's smile. The story ends with an emotional moment.