Mausam is the story of Amarnath Gill (Sanjeev Kumar), a medical student who sprains his leg while studying for his exams in Darjeeling. While being treated by Harihar Thapa (Om Shivpuri), the local healer, Amarnath has an affair with Harihar's daughter, Chanda (Sharmila Tagore). Although he tells Chanda that he will eventually return, Amarnath fails to keep his promise. 25 years later, a very wealthy Amarnath returns to Darjeeling for a vacation. Inquiring around Darjeeling about Chanda and Harihar, he discovers that Harihar has passed away and that Chanda had a daughter by Amarnath before going insane and dying. In an effort to compensate for his failures 25 years earlier, Amarnath decides to find Chanda's daughter, Kajli (also Sharmila Tagore). Although Amarnath has been told that Kajli has been sent to another town to study medicine, when Amarnath finally finds her, he discovers that she is a foul-mouthed prostitute living in a brothel.