Agatha Christie was a 20th century crime fiction novelist. Many of her stories feature the characters Miss Jane Marple or Hercule Poirot. Miss Christie is considered the best selling writer of books of all time. Her works are outsold only by Shakespeare and the Bible. Secret Adversary introduces the characters of Tommy and Tuppence who are included in several later books. In London in 1919 our two heroes are out of work and have decided to band together and try and find work. Tuppence procures work with a Mr. Whittington. When he closes his office and disappears without a trace the couple figures there must be more to the story.