Sam and Remi Fargo are used to hunting for treasure, not people; but a Texas oil baron contacts them with a personal plea. An investigator friend of the Fargos was on a mission to find the oil baron's missing father, and now the investigator is missing too. On a journey that takes them to Tibet, Nepal, Bulgaria, India, and China, the Fargos will find themselves embroiled with black market fossils, a centuries-old puzzle chest, the ancient Tibetan Kingdom of Mustang, a balloon aircraft from a century before its time, and a skeleton that could turn the history of human evolution on its head.