Holmes has been commissioned by Mycroft to unmask a medium who has beguiled one of Mycroft's agents. This Holmes completes in less time than allowed for one séance, but that is just the beginning of an adventure that brings Sebastian Melmoth into Holmes' purview. Melmoth is determined to learn the secrets of immortality. He is focused on the rites and rituals outlined in an ancient and priceless Egyptian scroll, stolen from the British Museum.