Thea Stilton and the Dragon's Code Geronimo's adventurous sister Thea takes center stage in this super special that's packed with mystery, adventure, and friendship! When Geronimo's sister, Thea, is invited to teach a journalism class at a college on Mouse Island, she has no idea that she's going to be called on to help solve a mystery. But when a student disappears, it's up to Thea and five of her students to find out what happened. A nail-biting mystery ensues, complete with secret passages, underground tunnels, and more than a few surprises along the way. Readers will love following the clues to help Thea and her new friends through their first adventure together!