The film deals with the story of two sisters – Mohini & Roop (both played by Nargis) – one legitimate, raised by a courtesan and one illegitimate. As time passes by, Roop falls in love with Raj Kumar Saxena (Raj Kapoor), an advocate, who is a tenant, comes to pay the house rent to her father, but instead meets Roop. Soon they become involved in a romantic relationship and Roop convinces her father for their marriage.
As the family plans to organise a party to formally announce the wedding, Raj runs into Mohini, Roop's twin sister and learns that Mohini is the real daughter. Unable to bear this, Mohini gets into an unpleasant situation and becomes angry with Raj. Meanwhile, Roop also learns the truth and tries to save Mohini by deciding to swap the positions of both of them. During this, the marriage happens where Raj unknowingly weds Mohini. When Roop's father becomes aware of this, he dies. What will be the next?