"When Paulina gets a phone call from home telling her that a friend is missing, the Thea Sisters travel to Peru to help solve the mystery. There, the five mice climb the Andes Mountains in search of a missing archaeologist. Along the way, they stumble upon clues leading them to a mysterious hidden city. Will the Thea Sisters find Paulina's friend, and the treasure of the Secret City?" -- P. [4] of cover.