Raj Raibahadur (Raj Kapoor) lives a wealthy lifestyle with his father, a widowed businessman. One day Raj is sent to work at the countryside Saraswati Dam. His father one day visits him and tells him how his deceased mother wished that he be married to Chandra (played by Vijayalaxmi), the daughter of his rich family friend. Raj decides to write a letter to Chandra which she completely ignores.
But Chandra’s younger sister Neelu (Nargis) acknowledges the letter and responds to it in Chandra’s name. After few letters Raj and Neelu fall in love, but Raj is still unaware that it is Neelu who writes to him. Just then Raj is diagnosed with tuberculosis, the same disease that killed his mother. Raj decides to pretend that he never loved Neelu and also insists that she should marry his physician friend, Dr. Kailash (Pran). He also flirts with Chandra to make Neelu believe that he does not love her. Chandra decides to end the suffering of her sister, who is sobbing for her love-loss. Upon learning the truth, Neelu accepts Raj as he is. Miraculously, Raj also turns well and both lead for a happy life.