The young college-going Shiva (Prithviraj Sukumaran) is extremely energetic and enthusiastic. Being very short tempered, he gets easily provoked by the rich, proud Vasu (Karthik Kumar) and his sneering attitude. From glares and snarls to punches and fights, Vasu and Shiva do it all, even for unreasonable, petty things. It is Shakthi (Shakthi Vasudevan) who stops their quarrels before they injure each other very badly. As he is friendly, kind-hearted and cool-headed, Shakthi tries to bring Shiva and Vasu together on friendly terms but in vain. Shiva, Shakthi and their faithful friend Bala stay together through thick and thin and are always ready to voice out their views on behalf of the hostelites in the college. Shakthi’s father (Bhagyaraj) often visits his son in the hostel and is like a father to all of Shakthi’s friends. Meera (Priyamani), the daughter of an M.L.A., nurtures a soft corner for Shiva. She is brave enough to stand up to him and check him when he throws unnecessary tantrums. Shalini (Anuja Iyer), Meera’s friend, is a shy, reserved Muslim girl from a very strict family background. She is often preoccupied with her own thoughts. Karthik (Jeeva) is a total show-off who tries to humiliate Shiva and Shakthi but ends up making a fool of himself.
The movie begins on an aeroplane as Shiva (a mature looking Prithviraj, with a French beard and rimless spectacles) heads back to his college to meet his friends. With his eyes sparkling with nostalgic memories, he takes a trip down memory lane and what he recalls about his college days forms the main part of the story.
At the reunion, the friends are happy to see each other after eight long years. But they all seem to be weighed down by a tragic incident: the death of Shakti. Shiva remains the most melancholic of them all. All goes well, until Shiva is found almost strangled to death. Everyone suspects Vasu, but Shakti's father discovers that the murder was attempted by Shalini.
In a flashback, it is revealed that Shakti and Shalini were lovers. In an ultimate twist, Shalini reveals that Shiva, who was running away from the police after breaking into an election booth, killed Shakti with chloroform, as the latter suffered from asthma. Shalini is upset that Shakti's father prevented her from taking revenge against the murderer of his son.
Shiva is cured and comes to seek apology from Shakti's father for accidentally killing Shakti. Shakti's father forgives Shiva and asks Shiva to marry Meera, who has been waiting for him for over eight years. Vasu also comes to seek apology from Shiva for all of his antics in college. Shakti's parents adopt Shalini, whose family has died, and decide to take her home. The film ends as Shalini says farewell to her friends and to the image of Shakti, who is forever present in the college campus. The message of the film goes for all of us: "Never forget the sweet memories that happened in college."