Blackmask Online: The Secret Adversary - Online text of Christie's story featuring Tommy Beresford and Prudence "Tuppence" Cowley. www.blackmask.com/olbooks/secaddex.htm
BookRags: And Then There Were None - Study guide with chapter summaries, character and object descriptions, author biography, quotes, topic tracking and discussion forum. www.bookrags.com/notes/none
Literature Network: Agatha Christie - Chapter indexed HTML pages of the The Mysterious Affair at Styles and The Secret Adversary. Includes a search feature. www.online-literature.com/agatha_christie
