A young adventurer and his Hindu man-servant arrive at a mysterious mansion in order to deliver the Moonstone, an amazing gem that had been stolen from a temple located deep in the Indian sub-continent. During the course of the night, the fabled jewel is stolen and Scotland Yard Inspector Cuff is forced to investigate a mansion full of suspicious and colorful suspects. Things become very serious when the thief resorts to murder and assault to cover their tracks which forces Inspector Cuff to solve this mystery before worse things happen.