Three friends and the successes achieved in their afterlife, due to one of their extraordinary friend.
       Two buddies Venkatramakrishnan and Sevalkodi Senthil set out in search of their long lost friend Panchavan Parivendan aka Pari. They have a nerd Srivatsan for company and through intermittent flashbacks we are told that Pari, a bright, yet free-spirited student, who through his charisma is able to convince his two friends to think for themselves, follow their heart and take challenges with a positive attitude chanting his mantra: all is well. Pari wants to change the education system and often lock horn with Professor Virumandi Santhanam the Principal whose says: "Life is a race - Run Run Run". He win the heart of Virumandi's daughter Riya and the film is about his journey.

Wildlife photographer Venkat Ramakrishnan (Srikanth) receives a phone call from his collegemate Srivatsan, better known as "Silencer" (Sathyan), telling him that their lost collegemate Panchavan "Pari" Parivendhan (Vijay) has been found. Venkat stops the flight and hires a car. Along with Sevarkodi Senthil (Jiiva), Venkat goes to their college water tank, where Silencer had asked them to come. After boasting about his success in life, Silencer reveals that he wants to know whether Pari won or lost a bet he made with Pari during their college-days which was to see who of the two would become the most successful. Then the trio go by car to Ooty, where Pari is believed to be. On their way, they recall their moments with Pari. Pari was a brilliant student, who believed in studying by understanding, while Silencer was involved in meaningless mugging. Venkat studied for his father's ambition of making him an engineer, burying his interest in Wildlife Photography, Senthil studies to improve his poor family's status and to make his elder sister get married. But Pari studied only to gain knowledge and for nothing other than that. Pari has a constant tussle with the college's principal Virumandi Santhanam (Sathyaraj), whom students fondly refer to as "Virus" and engages in mugging Pari. One day, when Virus doesn't approve the project of fellow student Paneer Selvam, Paneer commits suicide. Pari tells Virus that he is the cause for the suicide, thus making Virus write letters to the families of Venkat and Senthil. The fury and rage of Virus towards Pari grows more and more stronger when the trio break up to Virus's elder daughter Swetha's (Anuya Bhagvath) marriage and ends up caught by Virus and his younger daughter Ria (Ileana D'Cruz). Soon, Ria falls for Pari after seeing his kindness. Virus becomes more infuriated and asks Venkat and Senthil to go to Srivatsan's room, and asking them to cut their friendship with Pari. The trio ends up drunken in Virus's house as Pari proposes to Ria. Venkat and Senthil urinates the entrance of Virus's house and creates ruckus there. Meanwhile the trio pass their exams and Virus bets with Pari that none of Venkat or Senthil would get a job at the college campus interview and if they do, Virus will take off his moustache. Venkat goes to his father and tells him of his interest in wildlife photography and his father accepts it. Senthil gets job at the campus interview, and Virus gets his moustache off. The infuriated Virus creates a tough exam paper, specially made for Senthil to fail him. Ria tells this to Pari, and he and Venkat goes and fetches the xerox of the question paper from Virus's office. Virus comes to know this and expels the trio from school. Ria hears this and she tells that the deceased son of Virus committed suicide, due to Virus's enforcement of him to study engineering. Telling this, Ria leaves for her hospital. Meanwhile the pregnant Swetha goes into labour. When the ambulance stops due to heavy rain, Pari, Senthil and Venkat help Swetha get her baby successfully, thus making Virus reject the expel and gives him an astronaut's pen, a symbol of excellence. Pari and Senthil pass their exams while Venkat becomes a wildlife photographer.

Returning to present-time, Venkat and Senthil reach Pari's house, where they are shocked to see a different man with the name Pari (S. J. Suryah). Silencer tells them that when his secretary Lara came to Ooty to get the appointment for meeting Kosaksi Pasapugazh, the great scientist, he found Pari in a photograph. They go to Pari's house and asks the other guy where their friend is. He tells that, their friend is not Pari, but Pappu, and that the real Pari made fraud by making Pappu study engineering instead of him under his name. He reveals that fake-Pari, their friend is at Dhanushkodi. They go to Coimbatore and get Ria rid from an unwanted marriage and return to Dhanushkodi. They eventually reunite with their long lost friend, who is requested by Silencer to sign a declaration of defeat document on losing the bet. Venkat, Senthil and Ria ask their friend what his real name is, he tells them that it is Kosaksi Pasapugazh. Pasapugazh calls Silencer and reveals to him that he is the world-renowned scientist that Silencer had hoped to create a business deal with, proving Silencer had in fact lost the bet.