The term 'Middle Name in Mysteries' refers to the middle names of three famous fictional detectives: ALLAN (5 letters), Derr (4 letters), and CONAN (5 letters). The first name is ALLAN, which is the middle name of the famous detective created by Sir Arthur CONAN Doyle, Sherlock Holmes. The second name is Derr, which is the middle name of the detective created by Dashiell Hammett, Sam Spade. The third name is CONAN, which is the middle name of the detective created by Robert E. Howard, CONAN the Barbarian.