In this amazing adventure, Thea's friends the Thea Sisters head to Peru, where a good friend of Paulina's is in danger. There, the five mice climb the Andes mountains in search of a mysterious treasure that's hidden in the Secret City of the Incas. Readers will love following the clues to help the Thea Sisters solve the mystery! Geronimo's adventurous sister Thea narrates this fabulous adventure that's packed with action, mystery, and friendship!In this amazing adventure, Thea's friends the Thea Sisters head to Peru, where a good friend of Paulina's is in danger. There, the five mice climb the Andes mountains in search of a mysterious treasure that's hidden in the Secret City of the Incas. Readers will love following the clues to help the Thea Sisters solve the mystery!