Set in Calcutta during the 1950s, ''Mahanagar'' explores the evolving independence of middle-class women of the city. Arati (Madhabi Mukherjee), a homemaker, takes a job as a door-to-door saleswoman to meet the increasing financial pressure on her orthodox and conservative family, who share a cramped apartment. Despite the disapproval of her father-in-law, Priyogopal (Haren Chatterjee), the hesitant and nervous Arati soon begins to prosper in her field and gradually starts to enjoy her new-found financial and psychological independence.