The film deals with the story of two sisters—Mohini and Roop—both played by Nargis—the legal one raised by a courtesan and the illegal child. As time passes by, Roop falls in love with Rajkumar Saxena (played by Raj Kapoor), an advocate—who is a tenant—comes to pay the house rent to her father, but instead meets Roop. Soon they involve in a deeper romantic relationship, and Roop convinces her father for their marriage.As the family plan to organise a party to formally announce the wedding, Rajkumar runs into Mohini, Roop's twin sister and comes to know that Mohini is the real daughter. Unable to bear this, Mohini gets into an unpleasant situation, and gets angry over Rajkumar. In the meanwhile, Roop comes to know about the truth, and tries to save Mohini by deciding to swap the position of both of them. During this the marriage happens where Rajkumar unknowingly weds Mohini. When Roop's father comes to know about the reality he dies.