Agatha Christie's beloved spinster is back on PBS. Her first case: 'A Pocket Full of Rye.' Dame Agatha Christie remains the gold standard of mystery writers not only for her productivity -- the woman wrote 80 detective novels -- but also for her permanence. One could argue that Sherlock Holmes is the most universally famous detective, but Arthur Conan Doyle had but one iconic offspring while Christie had two -- Hercule Poirot and Miss Jane Marple.