Sherlock Holmes must unravel a complex murder mystery at Birlstone Manor after a coded warning arrives too late to save the victim. Holmes and Dr. Watson investigate the death of John Douglas, a man whose past life in a secret society holds the key to his brutal demise. The narrative shifts between the immediate investigation at the manor and a lengthy flashback detailing the events in a Pennsylvania mining town that precipitated the crime. Holmes faces the intellectual challenge of connecting a local murder to the far-reaching influence of his nemesis, Professor Moriarty. The story utilizes a dual-narrative structure to bridge the gap between the detective's present-day deduction and the historical context of the victim's hidden identity.

Readers frequently highlight the unconventional structure of this novel, which dedicates a significant portion of the text to a backstory set in America. Discussion often centers on the shift from the traditional English detective procedural to a gritty tale of industrial conflict and vengeance. Critics note that while the pacing changes abruptly, the connection to Moriarty provides a necessary sense of scale for the series. Fans of the canon appreciate the technical detail Holmes applies to the crime scene, even as they debate the effectiveness of the extended flashback. The book remains a subject of interest for those examining how Doyle expanded the scope of his detective stories beyond the confines of London.