River Heights is the site of a major international chess tournament. Two of the best young players in the world—Greta van Leeuwen and Donna Winston—are set to face off in a battle of wits and nerves. But as Nancy soon discovers, the action isn't just on the game board. First, someone deliberately ruins the opening ceremony. Then Greta's sister mysteriously disappears!

Greta must win if she wants to see her sister alive again, and as the tournament progresses, the tension builds. The kidnapper is a grand master of menace and deception, and it's up to Nancy to make all the right moves in this deadly game.