The film begins with an old doctor narrating the life of a courtesan Roshan Bai. The doctor is visited by her son Partha Bandopadhyay who has returned from abroad after becoming a doctor. The doctor gives him a box of jewels which his mother had left for him. In the box there is a photograph of Roshan Bai whose identity is oblivious to Partha. Partha leaves for Kolkata without taking the box stating that it would be of no use to him. Looking at Roshan's photograph, the doctor is reminded of his meeting with Roshan years back. Many years ago, the doctor was called to a courtesan's place to cure an ailing child. The doctor is told that the child is a Brahman. Roshan keeps looking at the child without giving away her presence. She performs for nawabs and eminent people on the other side of the child's room. One day the child sees her dancing in the hall. An enraged Roshan loses her composure and rebukes the child. The doctor intervenes and asks her the reason for such a reaction. Roshan then recounts the tale of her falling in love with a Brahmin priest years ago. Thinking of starting afresh, Roshan had requested her agent Sohanlal to allow her to quit her profession. He asked for a hefty amount which she was unable to pay fully. He let her go on the promise of further payments. Roshan presented herself as a poor Brahmin woman named Sharoma to the priest and won his confidence. Soon, they got married and led a happy conjugal life in spite of being poor. Roshan kept paying Sohanlal timely to maintain his silence. However, one day when she was not able to pay up, Sohanlal revealed her identity in front of her husband. Unable to cope up with the truth, the priest ran away. Sohanlal took Roshan back to the court. Roshan tried to commit suicide but was unable to do so because of her being pregnant. She wished her child would not have to live a life of shame like hers. She decided to keep her identity from the child. A Brahmin widow was hired to take care of the child as her own. Roshan would continue in her profession to make sure the child is given a proper education and a life of respect. After confiding in the doctor, Roshan requested him to promise her that he would take care of the child and his caretaker if anything were happen to her. The doctor readily accepts to do so. In the present, the doctor looks at Roshan's photo and reminisces. Calling her Sharoma, he says that her sacrifice has not gone to waste and her desire has been fulfilled.