This is the sequel to Andorra Man and Olduvai Man, and is the third in the trilogy. After two years living a tranquil life near the Olduvai Gorge in northern Tanzania 150,000 years in the past, John, Julie, and the kids find that they are no longer safe. Threats abound, and if they are to find a permanent home in which to find peace, they must first solve the mystery of Olduvai Man once and for all. Clues have led them to the shores of Lake Titicaca in northwestern Bolivia, circa 350 A.D., and here, with the help of Andy, Fiona, and a colleague fo John's from the Smithsonian Institution, they pack up and leave for the Mesoamerican city of Tiwanaku. Once there, however, the dangers do not diminish, and after making another discovery which only adds to the mystery, events unfold beyond their wildest dreams. They embark upon a journey that takes them from the temples of Tiwanaku to the plains of Nazca and on to the magnificent pyramids of Teotihuacan, leading them to an understanding of the universe beyond their wildest imagination.