Romesh Bhagwat Dogra alias Mamu (Irfan Khan) is the underworld don of Bombay, with unlimited contacts, and many judges, and almost the entire police force under his corrupt control. He comes across a young idealist young man, Krishna Patil (Manoj Bajpai), who is in training to be a police inspector. Mamu ensures that he fails. Then Krishan has a fight with a drunken and corrupt police inspector Ishwar Mohanlal Ghodbole (Mukesh Tiwari), and ends up beating Ghodbole badly. Krishna's dad, Ramakant (Anupam Kher) begs Ghodbole to forgive his son, and bribes him to leave him alone, but this does not stop Ghodbole from beating up two of Krishna's friends. Krishna enlists the help of rogue inspector Ajay Pandey (Om Puri), and a lawyer, Kavita Chaudhary (Tabu) to help bail his friends out, which they do. Krishna's sister, Mansi (Sheeba) then gets married to Divakar (Arshad Warsi), and shortly after this both die when the building in which they were living collapses, killing them and 54 other residents. The collapse of this building leads a trail straight to Mamu, and Krishna and his friends swear to kill him and anyone else who gets in the way, little realizing that by doing this, they are attempting to change a system that is corrupt to the core, and any such attempt/s to challenge it, leave alone change it is met with: - pain, suffering, and death.