A series of grisly murders rocks London. At each location, only a jumble of bones remains, along with a bizarre bone sphere covered in arcane symbols. The son of the latest victim seeks the help of Sherlock Holmes and Dr. John Watson, who discover a common thread that ties together the murders-and the persons responsible. 
Bizarre geometries-based on ancient schematics-point to members of a secluded cult. These men and women build strange constructs that will enable other-worldly creatures to enter our dimension, seeking sustenance. They are gaining so much power that even Moriarty fears that his empire is at risk-to the point that he seeks an unholy alliance with his eternal foe.