Shattered Glass - Glass series, #4

While trying to teach her adopted daughter, Reema, how to work with molten glass, Opal receives a letter from Master Magician Zitora Cowan requesting Opal's immediate help. Zitora resigned from the Sitian Council over two years ago to search for her lost sister, and no one has heard from her since. The letter is probably a trick, but Opal refuses to pass up the opportunity to help her mentor, who may be in genuine trouble.
Good thing Opal isn't that easy to fool. With her two soldier friends Nic and Eve providing backup, the three travel to a small town in the Jewelrose Clan. But can they rescue the Master Magician without being caught in the same trap?