Nemesis by Agatha Christie.

To me this is just one of the very best books she has written. A remarkable glimpse into the mind of a truly frightening old lady. One as adept at transplanting begonias as rooting out sleeping unseen evil. Ms. Marple recieves a a message, sent posthumously from Jason Rafiel a millionaire and ruthlesss business man she met briefly in a previous novel; A Carribean Mystery. He sets her a task, for which she will be richly rewarded should she succeed, to set right an unspecified wrong, to solve a mystery the world barely acknowledges. So off goes ms Jane Marple on a quest, a criminal pilgrimage, on a tour bus round the stately homes and gardens of Great Britain. sharing a bus with fellow travellers all the while believing evil stirs as she draws close to resolution.
             I believe this to be the last Marple Agatha Christie wrote. Although not the last to be published, that was Sleeping Murder. There is a dark melancholy at the heart of much of Agatha Christie's work. This novel is drenched in just such a mood, the cancerous ghosts of the past poisoning the now, disfiguring everything it touches. I think this book was published around 1971. The sixtes were over now, the long hot summer of love already seeming like an invented memory, not shared by all. Ms Jane Marple was getting older herself and though frail in body her mind was as sharp as ever.my favorite interpretation of the character being Joan Hickson (Although i will always reserve a special place in my heart for Margaret Rutherford. Not so much for being any one other than herself. Surely her greatest creation.) When I read Agatha Christie Ms Marple novels I see and hear Joan Hickson, her soft but precise delivery and those amazing eyes of hers. The eyes of a bird of prey. Eyeing her prey with steely precision until ready to deliver a wordy coup de gras. Delightful.