One moment, the lovely young woman was walking through the Battle of Hastings exhibition at the British Museum. The next, she lay dead on the checkered museum floor, a Norman arrow protruding from her breast. Inspector Lestrade believed he had solved the mystery, but almost immediately recognized that Scotland Yard needed the help of Sherlock Holmes.

From London to the Lake District, the master detective, along with his colleague Dr. Watson and recently-met American mystery writer, Anna Katharine Green, follows a string of clues that ultimately exposes the intricacies of a tragic love story—a woeful tale whose twists and turns reveal what Watson accurately called “the unhappiest of Holmes's adventures".