Oru Thalai Raagam is the heart breaking love story of Subhadra and Raja, played by (Roopa) and (Shankar) respectively. They are classmates and their colleagues includes Ravindran, Chandrasekhar, Kailash, Thyagu and others. The day start for them at a Railway Station, where they all catch train to the college. Raja sincerely loves Subhadra, but she does not reciprocate as she is an introvert as well as she is afraid of society's backlash. Moreover her mother's character is n't spoken good by the same people. Even though Subhadra loves Raja, she always tries to insult him whenever opportunity comes, but on positive side, she sometimes shows her feeling for him as well.
Raja's life becomes hell as he could n't concentrate on his studies and not taking care of his health as well and he gets affected by liver jaundice. Raja cuts a sorry figure among his colleagues and all of them want Subhadra to accept Raja's love. Later Raja's health deteriorates as he still neglect to have proper food and rest. Finally the college days are over for the batch and Roopa decides to proclaim her love. Roopa gets in the train and see Raja sitting in the compartment and she happily start speaking with him accepting his love and seek apology for her indifferent behavior, but it was too late as Raja is already dead.