Feluda and Topshe visit Lucknow and stay with Topshe`s father`s childhood friend, Dhiren. But their vacation takes a thrilling turn when a robbery is attempted of a priceless ring that was supposedly worn by Emperor Aurangzeb. The owner of the ring, Dr. Srivastav, confirms that nothing was stolen but apprehending worse, he requests Dhiren to keep the ring in his possession, to keep it safe.
However, in spite of their best efforts, the ring disappears from Dhiren`s possession. Felu, along with Topshe, starts investigating the disappearance, and in the course meet characters like Bonobihari, who lives with crocodiles and rattle snakes, and Mahavir, the son of Pyarilaal Seth, who had actually gifted the ring to Dr. Srivastav. While solving the mystery of the missing ring, Feluda uncovers the truth of Pyarilaal Seth`s death. But, will he, with the help of Topshe, be able to retrieve the missing ring?