Mukul (played by Kusal Chakravarty) is a young boy who is said to be able to remember events of his previous life. He stays up late into the night and draws sketches that he claims are of battles he had seen....展开His father decides to take him to Dr. Hajra (Sailen Mukherjee), a parapsychologist, for treatment. After listening to his descriptions of deserts and peacocks, Dr. Hajra guesses that the place Mukul describes might be in the deserts of Rajasthan, a state in western India. Mukul also mentions that he lived in the Golden Fortress (Sonar kella), though he can't explain what this means, and that their house had lots of gems. Dr. Hajra decides to take Mukul on a trip to Rajasthan hoping this may shed deeper light into such parapsychological phenomenon, , as well as help cure the young boy.
A newspaper report on Mukul and an interview with Dr. Hajra alerts two men by the names of Amiyanath Burman (Ajoy Banerjee) and Mandar Bose (Kamu Mukherjee), the villains in the story. Burman and Bose had earlier had encounters with Dr. Hajra, when he had exposed fraudulent activities of the pair. They interpret his mention of gems as a hidden treasure and plan to kidnap Mukul in hope of getting their hands on it. Their first attempt at the kidnapping fails when they pick up another boy, also named Mukul (Santanu Bagchi), from the same neighborhood. Mukul had already left for Rajasthan.
Alarmed by the failed kidnapping of his son, Mukul's father engages the service of Feluda (Soumitra Chatterjee), a private investigator, to help protect his son. Feluda accepts the assignment and leaves for Rajasthan along with Topshe (Siddartha Chatterjee). On the way to Rajasthan Feluda and Topshe meet Lalmohan Ganguly, a.k.a. Jatayu (Santosh Dutta), a popular thriller-writer, for the first time.
Meanwhile, Burman and Bose befriend Dr. Hajra, who is travelling on the same train but fails to recognise them. Dr. Hajra finds out that Mukul's father was a gemcutter, so the gems mentioned by Mukul have nothing to do with treasure. But Burman and Mandar Bose don't know this. They push off Dr. Hajra from a cliff and kidnap Mukul, with Burman impersonating as Dr. Hajra and Mandar Bose as a globe-trotter. Unknown to them, Dr. Hajra survives the fall, though he is forced to rest for a few days to recover from his griveous injuries. Feluda meets Burman, thinking him to be Dr. Hajra. Burman tries to kill him secretly using a poisonous scorpion, but fails. Jatayu joins them and they move around Rajasthan showing various forts (Rajasthan is full of Rajput forts) to Mukul, but none of them are the Golden Fortress. Meanwhile Feluda starts to suspect Mandar Bose after he boasts to Jatayu of having killed a wolf in Africa.
One night, Burman uses his parapsychological background to hypnotise Mukul, when he says that the fort was in Jaisalmer. The next morning, Feluda reaches the same conclusion after remembering that the fort of Jaisalmer was made of golden yellow limestone. However, when he returns to the guest house he finds that Burman has already left. Mandar Bose tells him that Mukul remembered the name of the place to be 'Burmer' (imaginary name). Feluda suspects foul play, and is confirmed when he finds that Burman has misspelled the word Hajra in the attendance register of the guest house. He leaves for Jaisalmer by car, but Mandar Bose leaves first and scatters broken glass on the highway, puncturing the tires of their car.
Feluda takes a camel caravan to the nearest train station, after failing to stop the train carrying Burman and Mukul midway. They take the next train to Jaisalmer. In the night, Mandar Bose tries to stab Feluda, but Feluda was only pretending to be asleep and has him at gunpoint. But suddenly Jatayu tries to recover Mandar Bose's knife, which was stolen from Jatayu. Using Jatayu as a shield he jumps out and hangs onto the side of the train, returning to his compartment. By chance, that compartment is occupied by Mr. Hajra, who frightens the drunk Mandar Bose. A swinging door pushes him out to his death.
The next morning, the three reach Jaisalmer and talk with Dr. Hajra. Then they go to the fort, to find Burman and Mukul searching the ruins. Burman has a phobia of peacocks and tries to shoot one, which angers Mukul into running off. At this point, Feluda confronts and captures him. He also tells him that there never was any treasure, whether rebirth exists or not. They find that Mukul is cured, and return to Kolkata.