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.