Emma's sister is missing. Her parents have spent all their money trying to find her and the family has moved to a trailer park for Crags \- magical creatures that live on the edge of human society \- next to the dark forest. Here Emma meets a smooth-talking cat named Jack who has a plan to rescue her sister. He shows her how to shape-shift, to develop claws and cat senses. But cat magic isn't easy, and Emma soon learns her sister is in the thrall of the faeries, the most beautiful and dangerous creatures of all.