In this book, Eustace, who was introduced as a character in The Voyage of the Dawn Treader, returns to Narnia with his friend Jill Pole. They, along with a Marshwiggle named Puddleglum, are sent on a quest to save a prince who has been bound by an evil magic. The prince happens to be the son of King Caspian (formerly Prince Caspian), who is now an old man. The prince has been taken captive by an enchantress reminiscent of the witch in The Lion, the Witch and the Wardrobe, and needs to be brought back to inherit the throne.