Once again, as in “A Study in Scarlett,” Arthur Conan Doyle reaches across the pond for material for a Sherlock Holmes story. In this case, it is a short story, about the long reach of the past and the legacy of the Ku Klux Klan in America. Three generations of Englishman face death from the grandfather’s involvement in the racist activities of the Klan. This is one of the few stories where, although Sherlock Holmes solves the mystery, he is late, much too late, in doing so.