 The Sinister Signpost by Franklin W. Dixon |  The Mark on the Door by Franklin W. Dixon |  The Haunted Fort by Franklin W. Dixon |  The Secret of Wildcat Swamp by Franklin W. Dixon |  The Secret Panel by Franklin W. Dixon |  The Sign of the Crooked Arrow by Franklin W. Dixon |  The Masked Monkey by Franklin W. Dixon |  The Yellow Feather Mystery by Franklin W. Dixon |  The Clue in the Embers by Franklin W. Dixon |  The Arctic Patrol Mystery by Franklin W. Dixon |  The Bombay Boomerang by Franklin W. Dixon |  The Secret of the Lost Tunnel by Franklin W. Dixon |  The Clue of the Screeching Owl by Franklin W. Dixon |  No Way Out by Franklin W. Dixon |  The Witchmaster's Key by Franklin W. Dixon |  Danger on Vampire Trail by Franklin W. Dixon |  The Wailing Siren Mystery by Franklin W. Dixon |  The Jungle Pyramid by Franklin W. Dixon |  The Clue of the Broken Blade by Franklin W. Dixon |  The Shattered Helmet by Franklin W. Dixon |