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.

Geronimo Stilton is the pseudonym of the famous Italian writer Elisabetta Dami. She has written the famous series of books on Geronimo Stilton. She co-owns the Italian based publishing company called Edizioni Piemme. She likes to get all her ideas through her travels to places around the world.