A marvelous mystery setup - one of Christie's best, in my view - is marred by just some relentless bigotry popping up in the mouths of people we are clearly meant to admire. Even Marple herself starts going on about heredity. Come on Jane. Hasn't all that time in St. Mary's Mead taught you anything? A pity, since the fog, the mysterious gunshots, the bizarre cast of characters and the looming threat of arsenic are all just what the doctor ordered.