Sherlock faces perhaps the most chilling enemy of his long career: the powerful and seemingly unassailable Culverton Smith, a man with a very dark secret indeed. Estranged from his best friend John Watson, Sherlock seems to have descended into hell.Sherlock faces perhaps the most chilling enemy of his long career: the powerful and seemingly unassailable Culverton Smith, a man with a very dark secret indeed. Estranged from his best friend John Watson, Sherlock seems to have descended into hell.