Claire Martinson and her sister Sophie are fighting to save Arden, the magical land they discovered by climbing up a chimney in their late aunt's house. They are the last descendants of Prince Martin of Arden, and only a prince or princess - with magic in their blood - can awaken the lost unicorns. As Claire struggles with her magical training, Sophie uncovers dangerous truths about the people they thought were their friends. Will Claire be able to prove she is the heir who was prophesied and unlock the magic of the unicorns - before it's too late?