London, 1890. 221B Baker St. A fine art dealer named Edmund Carstairs visits Sherlock Holmes and Dr John Watson to beg for their help. He is being menaced by a strange man in a flat cap – a wanted criminal who seems to have followed him all the way from America. In the days that follow, his home is robbed, his family is threatened. And then the first murder takes place.
Almost unwillingly, Holmes and Watson find themselves being drawn ever deeper into an international conspiracy connected to the teeming criminal underworld of Boston, the gaslit streets of London, opium dens and much, much more. And as they dig, they begin to hear the whispered phrase-the House of Silk-a mysterious entity that connects the highest levels of government to the deepest depths of criminality. Holmes begins to fear that he has uncovered a conspiracy that threatens to tear apart the very fabric of society.