Castle Glower has always been an interesting place to live. It sprouts new rooms occasionally and takes away rooms too. Young Princess Celie, the youngest of King Glower's four children, has been busy making maps of the castle and trying to keep up with the changes. One day Celie discovers a new passage way that leads to a new tower which has a nest containing a large red egg. Celie is the only one who can get to the new location because the passage goes away unless Celie is there. She is very curious about the egg and takes care of it until it hatches a griffin.Everyone thought griffins were only mythical beasts but now Celie has one to take care of. The castle also wants Celie to keep the griffin, which she names Rufus, a secret. She is able to tell her older brother Bran who is the Royal Wizard and their friend Pogue. Together they begin to search the castle for information about griffins.Bran has asked one of his old teachers to visit because the castle has added a room filled with weapons, some of which are magical. But instead of his old teacher, Wizard Arkwright arrives. The kids don't trust Arkwright because he seems to be too curious about their interest in griffins.This was an exciting middle grade fantasy with a strong, young female lead character in Celie. My only complaint is the cliffhanger ending which makes me want to read the next book right now. Fans of magic will really enjoy this series.