Mumbai Underworld tells the tale of two 12 year old boys (Vijay and Yakub) who grow up in the slums of India. Wanting to make a name for themselves in the mafia world, they start delivering drugs and loot people with the help of their transvestite friend. Things go wrong when they are sent to a juvenile reformatory after being wrongly convicted for a murder. They learn life is much tougher in the reformatory than the world they came from. They are tortured by the warden and senior inmates. But instead of reforming they develop a more sinister plan in their quest for ultimate power. Unexpected events force the two men to decide between redemption and their quest for power. Will they find redemption, if so, at what price?
