When the ghouls of Monster High follow Spectra Vondergeist one day, they discover a creeperiffic Ghost World with an all-spirit school. But their scary-cute student bodies are hardly welcome with the very strict Principal Revenant, and she punishes Spectra with frightful detention chains that prevent her from re-joining Monster High. Now, it's up to the imperfectly perfect friends to take on ghostly forms in order to save one of their own from disappearing forever.