It's the autumn of 1890, and a spate of bombings has hit London. Sherlock Holmes believes Professor Moriarty is behind the campaign of terror, but to what end? At the same time, a bizarrely garbed figure has been spotted on the rooftops of the capital. Known only by the name Baron Cauchemar, he appears to be a scourge of crime and villainy. But is he truly the force for good that he seems?