Arthur, a 12-year-old boy, has recently moved to a town and wants to fit into it. After suffering an asthma attack, he is saved by a mysterious metal object, called a Key, given by an even stranger character, Mister Monday, whose fellow Denizens bring an incurable plague to Arthur's town. Arthur hurries to the House, a mysterious structure that only he can see. Shortly after arriving in the House, Arthur discovers the structure of the house is a complete universe and is informed of his duty to unseat the seven Trustees who run the House, claim their Keys, and rule all of Creation. Arthur cannot live an ordinary life unless he overthrows all of the Trustees, who are also known as the Morrow Days. To do this, however, he must use the Keys, which infect him with sorcery and make him a Denizen