This film is adapted from the children's picture book of the same name published by American illustrator Maurice Sendak in 1963. The little boy Max (Max Records) is full of energy and has nowhere to vent. He is dissatisfied with the neglect of his sister Claire (Pepita Emmerichs) and the discipline of his mother (Catherine Keener). During a quarrel with his mother, Max ran away from home and drove a boat alone to the river. After sailing on the sea for two days and two nights, he arrived at a mysterious island. On the island lived a group of tall furry monsters with horns on their heads. Some of them were irritable, some were gentle, and some were timid. In order not to be eaten, Max lied to the monsters that he was the king of the Vikings and came to the island to be their king. The innocent monsters believed Max, happily worshipped him as king, and built a new house on the island. But what surprised Max was the conflict between the monster named Carlo (voiced by James Gandolfini) and the monster KW (voiced by Lauren Ambrose)...