The book is about at the end of the nineteenth century. The protagonist is a 14-year-old boy named Jay Berry Lee, who had enjoyed an idyllic childhood. Born to Missouri sharecroppers, he moves with his family to Oklahoma after his grandfather offers them free land. Daisy, his sister, has a crippled leg, and they devote much effort to gaining enough money to pay for reconstructive surgery. One day, while looking for their lost milk cow, Jay Berry discovers monkeys in a nearby river bottom. Visiting his grandfather's store, he learns that they have escaped from a traveling circus, which has offered a vast reward for their capture: $100 for the chief monkey, "Jimbo", and $2 each for the others. Jay Berry makes multiple attempts to capture them using traps and a net borrowed from his grandfather, but he gains only scratches and bites from them, at one point even losing his pants in the process.