Assistant Commissioner of Police Agnel Wilson recounts how he started investigating underworld gangster Sultan Mirza, tracing his journey from surviving floods in Madras to rising to prominence in Bombay. Despite efforts to keep Sultan in check, Agnel's investigation begins to unravel as Sultan temporarily hands over responsibility to his new recruit, Shoaib, the son of Sub-Inspector Khan.

Once Upon a Time in Mumbaai
In the dark alleys of 1970s Mumbai, a ruthless gangster's grip on power is challenged by a young and ambitious upstart, while a fearless detective puts everything on the line to bring them to justice.