Mystery Inc, Atem and his friends and Prince Adam/He-Man and his Masters of the Universe friends are invited at the grand opening of the Coolsville Museum of Criminology, displaying costumes of the monsters. However, a masked man creates havoc by stealing those costumes. Along the way after investigating Old Wickles Manor, The Flux Ghost 0, more costumes stolen and into the Coolsville Old Mining Town, they stop the masked man and his revival monsters
