Balaji and Mithun Luthria's Once Upon A Time In Mumbai is seen through the eyes of a police officer. It traces the changing face of Mumbai's underworld and how it all started. The film, set primarily in 1970's Mumbai, follows the rise of Sultan (Ajay Devgn), and the conflict when his protege Shoaib (Emaraan Hashmi), challenges supremacy and unsurps power to rule the murky underbelly of Mumbai.