In 1915, Sherlock Holmes is retired and quietly engaged in the study of honeybees in Sussex when a young woman literally stumbles onto 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. Under his reluctant tutelage, this very modern, twentieth-century woman proves a deft protégée and a fitting partner for the Victorian detective. They are soon called to Wales to help Scotland Yard fi...