In Sparkling Cyanide, Agatha Christie seats six--including a murderer--around a dining table set for seven, one year to the day that a beautiful heiress was poisoned in that very room. Six people sit down to a sumptuous meal at a table laid for seven. In front of the empty place is a sprig of rosemary--rosemary for remembrance. A strange sentiment considering no one is likely to forget the night, exactly...