Shiva and Indu are city-based students,who love each other. However, their love is strongly opposed by the latter’s parents. They're given a handwritten book titled "Pathinaaru" (Sixteen) by Indhu's mother to read. The book depicts a real-life story about two village teenagers Gopi and Ilavarasi, and their romance as they step into adolescence. Facing opposition from her affluent family, the gutsy Ilavarasi takes some bold unconventional steps, which backfires on her. The story of unrequited love and betrayal leaves Indu in a dilemma and she prepares to go with her family’s desires. But Siva is not ready to give up Indu and sets out to do his own investigation to get to the bottom of what ultimately happened to Gopi and Ilavarasi.