The hero of this picture book, Sam, has to wait for everything on the playground one day, and this makes him mad. He got madder and madder until he was the maddest he had ever been in his whole life. And then, suddenly, an unusual thing appears. It runs around, shoving and tripping and pinching and stomping, until all the other children have run away. It was hanging upside down from the monkey bars, grinning at him. Sam had never seen anything like it before, but he knew what it was. It was a Temper. At first, having a pet Temper is fun. But before long, the Temper starts causing trouble for Sam. And eventually, Sam comes to the realization that his Temper is something he needs to learn to control.