Join Thea Stilton and the Thea Sisters on an adventure packed with fantasy and friendship!The Thea Sisters are just about to head off on their separate family vacations when they receive a call from Will Mystery. Once again, there is trouble in one of the imaginary kingdoms! A crack has been discovered in one of the maps in the Hall of Roses. The girls head to the Crystal Kingdom to help uncover the mystery. There, they find that a dragon has been wreaking havoc all over the land. He has been turning all of their precious gems into stone and leaving a path of destruction whereever he goes. The sisters figure out why and help break the spell.