When a series of murders targets wealthy young women within a charismatic religious sect, Mary Russell must determine if the group is a spiritual movement or a cover for a lethal agenda. As a burgeoning detective operating in the shadow of Sherlock Holmes, Russell navigates the complex social landscape of post-World War I London to uncover the truth behind the New Temple of God. Her investigation forces her to balance her intellectual independence against the escalating physical threats posed by an elusive adversary. The narrative, presented through Russell's sharp, observant perspective, tracks her evolution from an apprentice into a formidable investigator capable of handling high-stakes danger.

This work is widely regarded as a sophisticated expansion of the Sherlock Holmes mythos, successfully shifting the focus toward Mary Russell's individual agency. Critics frequently highlight the author's ability to blend historical detail with a compelling mystery that challenges traditional genre tropes. The narrative is noted for its intellectual rigor and the nuanced portrayal of its protagonist's growth during a period of significant social change. Readers often appreciate the balance between the established Holmesian atmosphere and the fresh, modern perspective brought by Russell's character.