Sherlock Holmes and Doctor Watson are searching for the fifth Earl of Convarran who disappeared after returning to England following a disastrous excavation at the Black Pyramid in Dashoor, Egypt. During his investigation, Holmes discovers his clients are concealing a deadly secret, a secret that entangles him and Watson in a conspiracy that threatens all their lives. At the heart of the mystery are two ancient artifacts. Relentlessly pursued by cultists, collectors, and the British government, the artefacts are the key to finding the Earl. As Holmes unravels clue after clue, he is convinced that they all point to a single man. A powerful, dangerous man whom Holmes must confront and defeat if he is to find the Earl and save his clients.