It is 1897, and Sherlock Holmes is investigating a murder that took place during a society ball.

Holmes and Watson rush to the scene, but are shocked by the flippant attitude of the ball’s host: the wealthy Ernest Moncrieff, a favourite of high society who was found in a handbag as a baby. Suspicion naturally falls upon the party guests, but the Moncrieff family and their friends – including the indomitable Lady Bracknell – are more concerned with the inconvenience of the investigation than the fact that one of them may have committed murder. But behind the superficial façade, Holmes and Watson uncover family secrets going back decades, and a mysterious blackmailer pulling the strings…