When a prominent archaeologist is murdered upon returning to England with a potentially explosive historical document, Mary Russell must navigate a web of academic rivalry and religious intrigue to uncover the truth. Russell, a brilliant and unconventional partner to Sherlock Holmes, takes on the investigation after the victim is found dead in her own home. She faces opposition from those desperate to suppress the contents of the letter, which claims to be written by an apostle of Christ. The narrative unfolds through Russell's sharp, analytical perspective, capturing the social tensions and intellectual atmosphere of 1920s England.

This installment in the Mary Russell series is often noted for its successful blend of historical research and traditional detective tropes. Readers frequently highlight the intellectual chemistry between Russell and Holmes as a primary draw for the series. The narrative structure is praised for its ability to weave complex theological questions into a standard murder mystery framework. The setting is consistently described as atmospheric and well-researched, providing a grounded backdrop for the high-stakes investigation. The work is generally regarded as a solid entry that maintains the established character development of the series.