In this third book following The Book of Three and The Black Cauldron, Elionwy is sent off to the Isle of Mona to learn to be a proper princess with the royal family there. Taran and Prince Gwydion accompany her and try to protect her, except "protection" in their minds is not telling her anything about the dangers they've learned are after her and instead just ordering her to behave herself, a course of action which of course is stupid and ends up with Elionwy going off in a huff and getting captured, and then having to be rescued. Yes it's a kids's book but still very annoying for all the characters to act like such idiots. :p In the end Elionwy discovers a bit more about her heritage and the magic powers she's heir to, and Taran discovers he has a crush on the princess.