Baidurya Rahasya (Mystery of the Electric Gem) is a Bengali thriller movie directed by Tapan Sinha. This movie was released on 8 May 1985 under the banner of Saraswati Chitram. Storylining and music direction was also done by Tapan Sinha.

An invaluable emerald was stolen from a Lord Krishna's temple in an island, that was insured for Rs. 8 lakhs. The insurance company appointed Hindusthan detective agency for investigation. The Head of the Detective agency Mr. Madan Bose went to the temple with his assistant to meet the Mohanta Maharaj of the temple. On the other hand, two young ladies went to the temple as devotees of lord Krishna. Without informing the local police they started investigation secretly. There are some mysterious people like young researcher, priest Nityananda, and Singh ji, trustee of the temple. When old garden keeper Charandas was brutally killed by a masked man in the night, the police started a parallel investigation. Finally it was revealed that not only theft but another murder was committed in the temple few days ago. The true culprit was identified and the jewel retrieved at last.