Karthik (Vijay Antony) is a brilliant student but already shows signs of criminal behavior at childhood itself, like forging his friend's parent's signature on a mark sheet. Sent home from school early for this misdeed, Karthik is shocked to discover his mother (Charmila) in bed with his uncle. His mother begs him not to tell his father, but he does so, and his father commits suicide. Karthik's mother and uncle continue their relationship; Karthik then kills his mother and uncle by setting the house on fire. He is sent to a juvenile home where he grows up. On his release, the warden gives him the address of another of his uncles and asks him to concentrate on his studies.

Karthik's aunt is not interested in taking him in, so he goes to Chennai to start a new life. As fate would have it, the bus meets with an accident, and his co-passenger, Mohammed Salim (Ratchasan Saravanan) eventually dies. Karthik steals Salim's documents, adopts his identity, and due to his high marks of Salim, enrolls in a Government medical college in MBBS. He develops friendships with a rich class mate named Ashok (Siddharth Venugopal), his girlfriend Rupa (Rupa Manjari), and their friend Suresh (Vijay Victor). Ashok allows Karthik to stay in his house rent-free, seeing his innocent and good nature. Later, Salim and Ashok encounter the same warden from the former's juvenile home, who seems to recognize Karthik. However, since Karthik is now impersonating Salim, he picks an argument with the warden and swears that he is not the person he thinks. This incident causes Ashok to develop a dilemma towards Karthik's identity.

One day, Ashok and Suresh plan to go to a farmhouse without Rupa. Suresh suggests that they take some other girls along. Karthik lets Rupa know of this plan due to her sincere and true love for Ashok. Rupa starts to suspect Ashok's fidelity, and Ashok worries that Karthik betrayed him by complaining about him to Rupa. Ashok slaps Karthik angrily and asks him to get out of his place. Karthik, seeing no other way, apologizes to him and looks for another lodging.

Ashok is still full of suspicion. While Karthik takes bath, Ashok opens his briefcase. He finds a photo of Karthik's biological father and realizes that it was a different man who Karthik had introduced as his actual father earlier. Suddenly, Karthik enters the room and asks Ashok to give back the photo. Ashok refuses, removes Karthik's towel, and confirms that he is not a Muslim, as he was not circumcised. Karthik gets angry and pushes Ashok; Ashok hits his head on a table and dies. At first, Karthik is shocked and depressed by this unexpected accident, but he then covers up the murder by burying Ashok's body in a graveyard at the outskirts, so intelligently that no one ever finds out that Ashok is dead. When a family friend of Ashok's, who has seen Ashok only in his childhood, plans to meet him, Karthik successfully impersonates Ashok in front of Ashok's own parents and Rupa.

Suresh, however, discovers Karthik's deception. Karthik then kills Suresh and buries him at the same graveyard. The following day, the police come to Ashok's house and reveal that they have found Suresh's corpse. They interrogate several people in the city including Karthik, but they cannot find the truth. They conclude that Ashok killed Suresh due to an old personal vengeance and then absconded; meanwhile, they consider Karthik (now back to impersonating Salim) as an innocent and a hard-working student. Karthik continues to live as Salim, after seeking permission from Salim's father and promises to take care of him forever. The film ends with the tagline "To Be Continued", and the story of Salim (Karthik) becoming a successful doctor is shown in its sequel movie, Salim which was released in the year 2014.