The theft of a sacred yellow diamond during a birthday celebration triggers a complex investigation that exposes the hidden secrets of an aristocratic household. Rachel Verinder inherits the Moonstone, a diamond with a violent history, only for it to vanish from her bedroom on the night of her eighteenth birthday. The narrative unfolds through a series of accounts provided by various characters, including servants, lawyers, and family members, who attempt to reconstruct the events of that night. As the investigation progresses, the protagonist and those assisting her must navigate social expectations, colonial anxieties, and the physical constraints of the isolated country estate. The story utilizes an epistolary framework to present multiple perspectives, forcing the reader to weigh the reliability of each narrator against the objective facts of the crime.

Readers frequently highlight the innovative structure of the novel, noting how the shifting perspectives create a layered reading experience. Discussion often centers on the effectiveness of Sergeant Cuff as a prototype for the modern detective figure. Critics often point to the balance between the intricate plot mechanics and the social commentary regarding Victorian morality. Many readers appreciate the atmospheric tension that builds as the mystery deepens, though some note the pacing can feel deliberate by contemporary standards. The work remains a foundational text for the genre, consistently analyzed for its influence on subsequent detective fiction.