One strange stone! Two feisty friends! A majestic mountain! Lots of llamas! And a topsy-turvy train ride! 

Christina and Grant get the chance of a lifetime to visit Peru and the incredible Incan ruins at Machu Picchu. "How did they build this amazing place?" Christina wonders. 

Along the way, they meet two Peruvian kids looking for their lost llama, and soon, they step into a mystery filled with a terrifying train ride, baffling artifacts, a fierce Inca king, and even some splattering, smelly llama spit! Will they find out who — or what — is scaring tourists away from the majestic mountain city of Machu Picchu? Read and find out!