Karunakaran finds it difficult to adjust with the society that he lives. As a result, he is unable to control his anger and ends up with trouble due to his unpredictable behavior, which becomes a constant worry for his mother and brother. A series of incidents force him to leave Madurai and end up in Chennai. Despite scoring high marks in school, he joins a local arts college in the city and stays in a hostel, where trouble begins. Aarthi, a medical student and the younger sister of Karuna's sister in-law, develops a soft corner for Karuna.

Meanwhile, ACP Marimuthu, Inspector Rajendran, SI Selvam, and HC Perumalsamy witness a car accident in the outskirts of Chennai. When they are about to take the victim to a nearby hospital, they come across a huge stash of cash. The policemen kill the half-dead victim and flee to Chennai with the money. However, Maya, a prostitute, learns the truth by overhearing Marimuthu's telephone conversation and records it. When Maya plans to threaten Marimuthu, she accidentally loses her camera which had the video footage. The next day, Marimuthu gets a threatening call from a guy and finds out that it was Maya who recorded his conversation. An enraged Marimuthu beats up Maya and eventually kills her.

A sincere cop named Palaniammal takes up this case. In the college where Karuna studies, there is a series of thefts happening in the hostel. Marimuthu finds out that one of the college students had actually stolen Maya's camera. One day, a bag containing all the stolen items is kept in Karuna's hostel room, making him as the prime suspect of all the threats, which leads him to get arrested. Marimuthu, along with his friends, kidnaps Karuna and Maya's friends with plans of killing them in a forest. They kill Maya's friends, but Karuna escapes from there and reaches Chennai. Meanwhile, Marimuthu finds that it was not Karuna who had blackmailed him. Karuna is falsely accused of mental instability by Marimuthu and his team of policemen and is institutionalised.

Karuna is kept under constant sedation with the help of a corrupt doctor. They forge a story that Karuna is suffering from a mental disorder which makes him think that he is being chased by a group of policemen for a fake encounter. Karuna escapes from the mental asylum and reaches his hostel. Karuna kidnaps Rajendran and threatens him to disclose all the truth to the public. Meanwhile, Palaniammal collects vital info and cracks the case. It is revealed that the person who stole Maya's camera was Dinesh, who happens to be the son of the college principal. Knowing this, the principal had tried to save Dinesh by keeping all the stolen items in Karuna's room during vacation, so that Karuna will return the things and all will be done.

When Palaniammal corners and is about to arrest the culprits in the college old auditorium, she gets a call from the commissioner that the person, who was murdered by Marimuthu and his team was a leading politician in Bangalore which could lead to state problems and hence does not disclose the incident to the media. Palaniammal is helpless and leaves the place. However, Karuna gets enraged and kills Marimuthu, Rajendran, Selvam, and Perumalsamy, where he is sentenced to psychological treatment (as he is falsely believed to have a mental disorder). After getting released, Karuna and Aarthi get married, where he works as a teacher in a deaf-dumb school.