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!