Oru Naal Koothu revolves around a few characters who are all connected by one thing — marriage. There is Raj Kumar (Dinesh, unconvincing), whose colleague and lover, Kavya (Nivetha Pethuraj, impressive in her debut), is about to get married to another guy. She still loves him, but he wants her to wait because he has a family (which he admits he doesn't love, but has a responsibility towards) to taver mais...