Sir is a crime drama. The movie follows the story of a Mumbai-based college lecturer Amar Verma (Naseeruddin Shah), who lost his son Kunal when the gang war between the crime lords - Veljibhai (Paresh Rawal) and Chhapan Tikli (Gulshan Grover), broke out in Mumbai. Since then, he has devoted his entire time to his students. Years later, Amar meets a student named Pooja (Pooja Bhatt), who has a stammering problem and decides to help her out. Things get complicated when he finds out that Pooja is the daughter of Veljibhai. He decides to talk to both the gang leaders to convince them to agree to have peace between the gangs, they agree to it. However, is everything as simple as it seems? Did Amar really succeed in convincing the gang lords or just created more problems for himself?