A cryptic message leads Sherlock Holmes to investigate a brutal murder in a Sussex manor, uncovering a connection to a shadowy criminal organization. Holmes and Dr. Watson must navigate a complex web of deception that spans from the English countryside to the industrial coal mines of America. The narrative employs a dual-structure approach, shifting from the immediate investigation in England to a lengthy flashback detailing the history of a secret society. Holmes faces the intellectual challenge of his career as he attempts to dismantle the influence of Professor Moriarty.

Readers frequently highlight the distinct split in the narrative, noting that the second half functions almost as a standalone prequel to the main mystery. Discussion often centers on the effectiveness of the shift from the traditional London detective setting to the rugged American frontier. Critics observe that the book serves as a significant expansion of the Moriarty mythos within the canon. Many readers appreciate the darker tone compared to earlier stories, though some find the transition between the two halves abrupt. The work remains a focal point for those interested in the evolution of the detective genre and the development of the Holmes-Moriarty rivalry.