Thirteen-year-old Gregory Buchanan receives a letter from his Uncle Max and tells his friend Brian, Uncle Max "lives in kind of a different world from the rest of us." Gregory and Brian discover just how different that world is when they accept Maximiliam Grendle's invitation to visit. The two boys discover a game board in the nursery and are swept into competition. But who is their competitor? There are no apparent rules to this Game, either. The mysterious and frightening Jack Stimple gives pointers, but refuses to reveal the rules. The Game takes the boys to fantastic places in the woods around Grendle Manor: Clock Corner, the Petroglyph Wall, Fundridge's Folly. They encounter an axe-wielding troll named Kalgrash, an ogre called Snarth, and a tiny man, Wee Sniggleping. As the boys advance in the Game, additional locations on the game board appear and they discover the mythical people for whom they compete.