Dame Agatha Christie (1890-1976) is the best-selling novelist of all time and the writer the world calls the "Queen of Crime." Born Agatha Miller in Torquay, Devon, she came to fiction on a dare: her sister Madge bet she could not write a convincing detective story, and the result, The Mysterious Affair at Styles, introduced the Belgian detective Hercule Poirot. Her dispensing work in a hospital pharmacy during the First World War, repeated again during the Second, gave her the expert knowledge...