The king's soldiers are powerless to protect him from the fearsome monsters he keeps seeing around him, until Peter points out exactly where they are coming from and what their true nature is.
As a kid, I was simultaneously entranced and creeped out by this book. As an adult, I realized that I was a weird kid and there's nothing remotely scary about this book. It's a fun, silly story with fun, silly illustrations. It's a solid addition to a bookshelf if you find it for pretty cheap or an enjoyable book to check out from the local library sometime.