Babu is a thief in Bombay released from prison after serving a sentence. He is welcomed by his friend and partner-in-crime Balli who has set plans in motion for a bank robbery. He gives Babu keys to a car, as he has to play the role of a rich man in the heist. There is a curious ring attached to the key which piques Babu’s interest. When asked about it, Balli tells him that the ring is his only connection to his long lost parents. He had become separated from them when he was five years old, and since then has not managed to find them.
Babu is being tracked by Inspector Malik who is also his old school friend. They had stolen something as children and been caught. Malik’s rich father had managed to get him off, but the poor Babu was branded a thief for life. Malik sees the potential in Babu to lead a better life and wants him to leave the ways of crime. While he refuses on the surface, Babu is deeply affected by Malik’s words. He tells Balli that he wishes to leave behind his criminal activities. This causes Balli and the other gang members to become suspicious. When the other gang members are suddenly arrested by the police, Balli is sure that Babu informed on them. He confronts Babu and a struggle ensues between them. In the fight, Balli suffers a fatal injury. A scared and guilt-ridden Babu flees from Bombay to Jogindernagar.
In Jogindernagar he meets the wily Bhagat. Bhagat soon realises that Babu is unusually afraid of the police and guesses that he must have a criminal past. He takes Babu to a village where he shows him the house of the richest man there. Apparently the family had lost their son many years ago and have been looking for him ever since. He wants Babu to pretend to be their son Kundan and infiltrate the house to steal their money and jewellery. Babu agrees and with Bhagat’s help is able to convince the family that he is indeed Kundan. The family are overjoyed to have their son back and shower him with affection. Babu is affected by the genuine love he receives from them, especially Kundan’s blind mother. He is also intensely attracted to Maya, who is supposed to be his sister. Bhagat continues to pressure him to complete his objective. But the more Babu lives with the family, the less willing he becomes to do the job.
Meanwhile the Bombay police receive word that Babu had been spotted in a Delhi railway station and start looking for him in earnest. Maya becomes troubled by the unusual nature of Babu’s attentions, and one day follows him when he goes to meet Bhagat. She learns of Babu’s identity, but also his unwillingness to steal from her family. Her marriage has also been arranged and expensive jewellery has been bought for the wedding. Bhagat blackmails Babu to force him to steal the jewellery.
In a tragic twist, Babu learns that the real Kundan was his late friend Balli. When he refuses to go through with the robbery, Bhagat and his accomplices beat him up and take the jewellery anyway. Maya’s wedding is to happen on that day and the loss of the jewels endangers its prospects. Babu chases after them and is able to return the jewels in the nick of time. As the wedding progresses, Inspector Malik arrives on the scene. He is happy to see that Babu has genuinely changed and lets him stay on in the family as their son. As Babu finally accepts life as Kundan, he tearfully bids farewell to Maya.