Bridget, a friend of the Thea Sisters, goes missing in Scotland. The Thea Sisters go to Scotland to find their friend and encounter Celtic legends, cryptic messages and hidden treasures.
Geronimo Stilton's vacation plans are interrupted by the entire Stilton clan and a treasure hunt in the Black Hills of South Dakota, where he takes a hot-air balloon ride to Mount Rushmore.
Colette's five friends are excited to see the Eiffel Tower and attend her cousin Julie's runway fashion show when they all spend spring break in Paris, but upon their arrival, Julie's designs are stolen, and the Thea Sisters take the case.
Creepella von Cacklefur visits Squeakspeare Mansion with her niece, Shivereen, and meet Bobby Squeakspeare, a descendent of the famous William Squeakspeare, but the mansion is filled with spooky ghosts.
Paulina and the Thea Sisters journey to Peru to find their missing archaeologist friend, but as they ascend the Andes Mountains, the sisters find clues that lead them to a mysterious hidden city.
The Thea sisters learn about a mysterious shipwreck off Whale Island from their history professor, who disappears, prompting the sisters to search for him and the legendary treasure they think he was searching for before he disappeared.
