Two brothers discover an oblong box in the park, which they dismiss as "just some dumb old game." The boys turn their attention away from the game's "jungle adventure" board to discover a second game board inside with an outer-space theme and a colored path leading to the purple planet, Zathura. Mayhem ensues each time one of the boys draws a game card or rolls the dice. Facing meteors and giant robots, the brothers begin to appreciate each other and their sibling rivalry dissolves.