The Thea Sisters are about to head off on their seperate 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 a map in the Hall of Roses.

The mouselets head to the Crystal Kingdom, where a dragon has been wreaking havoc all over the land. He has been turning all of the precious gems into stone and leaving a path of destruction wherever he goes. Can the sisters figure out why the dragon is destroying the Crystal Kingdom and stop him before it's too late?