David Eutychus Walker, a recently orphaned autistic sixteen-year-old and a chess savant living with his clinically reticent uncle, only plays chess online where there is no personal contact with his opponents. His favorite adversary is a mysterious stranger who goes by the chess handle gringo666. At first, both players are in it only for the game, not to make friends, but as their competition sharpens, they begin to exchange text messages against the wishes of David's uncle.
Gringo666's fascination with David heightens when he learns that David and his uncle plan to travel to Bolivia to visit a scenic lake—Lake Titicaca—which the boy first sees in a photo from a Bolivian girl and her mother, whom his late parents sponsored through a charitable organization. David is not so much interested in the girl, but is drawn by the beautiful, clear-blue lake. When they arrive in Bolivia, however, David and his uncle find that they must not only deal with altitude sickness and treacherous terrain, but also a hostile population and a sinister plot that may explain why gringo666 has suddenly taken such a keen interest in the young boy.
When David and his uncle are mistakenly kidnapped, it becomes clear that their very survival depends on aiding the Bolivian government in tracking down a political enemy who has taken refuge in the United States. Pushed to the limits of their endurance, and their lives, can David's knowledge of chess ultimately save him and his uncle from a deadly fate and in the process force gringo666 to finally reveal his true identity?