Pushpa (Sharmila Tagore) is kicked out of her house by her husband and his new wife. When she refuses to leave, he beats her and throws her out. She goes to her mother for help but her mother too, disowns her. When she tries to commit suicide, she is sold to a brothel in Calcutta by her village-uncle, Nepali Babu (Madan Puri). On her audition at the brothel, Anand Babu (Rajesh Khanna), a businessman seeking love, is attracted by her singing. Anand Babu is unhappily married and lonely and becomes her regular and exclusive customer as love blossoms.
Later a widowed man with his family, from the same village as her, moves in close to Pushpa's place. The new neighbour's son, Nandu, doesn't get any love at home, as his father works all the time and his stepmother doesn't care about him. Nandu's father finds out about Pushpa's new life and forbids her from interacting with him and his family as he fears what people would say. However, Pushpa starts treating Nandu as her own son when she gets to know that he is mistreated at home, and often goes hungry. Nandu also comes to love Pushpa and starts to regard her as his mother. He visits her every day and comes upon Anand Babu who also becomes fond of him becoming a father figure, calling him Pushpa's son, seeing the way Pushpa loves the child.
One day, Anand Babu's brother-in-law comes to see Pushpa and demands that she tell Anand Babu to stop visiting her. With great reluctance, Pushpa agrees and she turns Anand Babu away when he comes to see her. It is then that businessman realizes that he is in love with Pushpa. When Nandu suffers from fever and his treatment is too expensive, Pushpa asks Anand Babu for help and he secretly finances the treatment and does not let anybody know. When the doctor asks him why is he so keen on helping Nandu, he replies some relationships have no names. However, when Nandu's father asks the doctor who paid for the treatment, the doctor says that his mother did. Then Nandu's father finds out that it was Pushpa who saved her son's life and he thanks her and gives her the sari that he had bought for his wife, telling her that it was gift from a brother to a sister. A touched Pushpa accepts.
Nandu's family has to move to the village and Nandu plants a sapling of nigh-flowering jasmine (Harsingaar or Parijat) at Pushpa's home, making her promise to always take care of it. Pushpa cries and agrees.
Several years later, Nandu grows up to become a government engineer posted in the same town. Anand babu meets Pushpa, now working as a maid servant who is ill-treated and they both reconcile. Nandu unsuccessfully searches for her and gives up after inquiring in the neighborhood. Nandu's son gets sick and they go to the same doctor. Meanwhile, having met Pushpa, Anand babu decides to catch up with all his old friends and meets the doctor. During conversation, he reveals he has stopped drinking and visiting brothel once he left Pushpa. He also tells him that he is now divorced/separated due to his wife's partying ways but is finally at peace and is happy with Pushpa's love and affection in his heart. They talk about Nandu and the Doctor informs him that Nandu is in town. Nandu meets Anand babu when he comes to meet the doctor to ask regarding the medicine, who takes him to meet Pushpa. Both of them, unable to see Pushpa ill-treated, stand up for her and in the end Nandu takes Pushpa home with him, like a son who is reunited with his long lost mother with Anand babu looking on, crying happily