Roxy Norrington and her pet bloodhound, Artu, have been named co-benefactors in sharing the fortune of the late Colonel Beauregard, who promised to remember them in his will. But there is one catch: the duo--along with four other heirs--must spend one night in a haunted castle on a remote island named Mystery Island. During their night on this haunted isle, Roxy and Artu--along with the rest of their Super Sleuth comrades--are suddenly thrown into a world of trouble when it is discovered that they are being targeted by a duo of ghosts called the "Phantom Shadows." Before too long, the gang finds themselves having to find and rescue Roxy and the other heirs--but will they be too late to stop the Phantom Shadows before they succeed in a mass execution?"