Karan Mehra, a young man, lives with his mother, whom he believes to be a widow. For fifteen years, he lived under the impression that his father was dead. In the present, his mother finally tells him the truth—his name is Karan Khanna, and his father is alive in prison, sentenced to life for murdering a dancer named Mala fifteen years ago. To the end, his father had pleaded his innocence. Unwilling to associate such a stigma to her young son, Karan’s mother had left with him for Bombay, a city where none would know of her husband’s crime.
Once he knows the truth, Karan goes to see his father in jail. To his great disappointment, his father treats him coldly, having grown bitter over years in prison with no visitors and no letters. He tells him yet again that he is innocent of the crime for which he had been convicted. Convinced by his father’s protestations, Karan vows to prove his innocence. This prompts the old man to embrace his son.
Karan returns to Bombay and goes to a newspaper office to begin his investigation. Digging up old files, he reads the whole case carefully with the help of Asha, a young reporter for the newspaper. As they work together, the two fall in love.
From the newspaper reports, Karan traces the only witness who had defended his father—a grocer by the name of Ramdas. When he meets Ramdas, the man tells him that he had seen his father standing next to Mala’s body, but he picked up the bloodied knife from the floor only once Ramdas had arrived. When Inspector Mehta, the officer in charge arrived, he dismissed Ramdas’ claims on grounds of him being short-sighted. His testimony was ruled inadmissible by the court. However, the police inspector Mehta soon realized that Ramdas was correct. After Karan’s father was convicted on the evidence of two chief witnesses, Kishori, a dancer, and Jumman, Inspector Mehta overheard the two talking. He heard them say that Kishori, an eyewitness to the murder, had been paid off by the real murderer to pin the blame on Karan’s father if she wished for him to support her all her life. Unfortunately, before he could get hold of the letter, the police officer was silenced by the public prosecutor Rai Bahadur Jaswant Rai.
At present, Kishori is still a well-known singer and dancer. Karan cultivates her acquaintance until he becomes a regular visitor at her house. He convinces her that he is in love with her, and the woman takes a liking to him as well. However, Kishori soon realizes that Karan’s only intent is to secure the letter and flies into a rage. Karan rebukes her, reprimanding her for having sentenced an innocent man to prison for fifteen years. Ashamed, Kishori hands Karan the letter. He reads it to find out that a certain Diwan Sardarilal had killed Mala. When he takes the letter to Jaswant Rai, he burns it down.
Karan tells Asha of the events and the two take to the streets to protest the injustice. Asha conducts a campaign in her newspaper as well. It is revealed that the letter Kishori had provided earlier was fake. She comes to hand Karan the original letter, which is reproduced in the newspaper. The case is reopened. Karan’s father is ultimately acquitted and the real murderer convicted.