The novel is about Conrad, a young boy, who spends each Thursday afternoon with his uncle, Mr. Ringelhuth. One Thursday — it happens to be the 35th of May — they meet Caballo, a black horse that can speak, is well-versed in German literature, and at the same time, is the best roller skater in the world. Together they enter Mr. Ringelhuth's huge wardrobe, which stands in the hallway, and end up in a series of magical lands, starting with the land of Cockaigne, followed by a medieval castle complete with jousting, an upside-down world in which children send bad parents to reform school, a science fiction nightmare city with mobile phones and moving walkways, and a South Sea island. On his return to the real world, Conrad writes a school essay about his experiences.
