The magic of the mirror

"The Thea Sisters are enjoying a beautiful spring afternoon when they receive a secret message from Will Mystery. They are being called back to the Seven Roses Unit. They are heading on the most important mission they have ever been given. A powerful magic mirror has been found, and someone wants to use it for evil! The mirror has the power to . . . turn all of the fantasy kingdoms into dry deserts. The mouselets must do something to stop it!"--Back cover.