In 1915, Sherlock Holmes is retired and quietly engaged in the study of honeybees when a young woman literally stumbles into him on the Sussex Downs. Fifteen years old, gawky, egotistical, and recently orphaned, the young Mary Russell displays an intellect to impress even Sherlock Holmes—and match him wit for wit. Under his reluctant tutelage, this very modern twentieth-century woman proves a deft protégée and a fitting partner for the Victorian detective. But even in their first case together, the pair face a truly cunning adversary who will stop at nothing to put an end to their partnership.