As a child, Catherine Taylor never understood why her parents were so secretive and distant. After the death of her grandmother, Cat's parents take her to a mysterious castle called Blacklune. They explain to her that they, and she, are vampires, part of a hidden community co-existing with humans. Now that she's of age, Cat will be initiated into the community and undergo a period of training in its methods and morals, along with several other vampire students her own age. At Blacklune, Cat meets a young man who had appeared to her in dreams, Morgan. She and Morgan form an instant bond, but success with their vampire lessons doesn't come so easily. Tempted by the lure of blood and the powers they now have, Cat and Morgan push the limits over and over, ignoring the concerns of their classmates and the scolding of their teacher, River. As they become ever more reckless, Cat and Morgan risk going too far. It's only when serious harm comes to someone else that they realize they have to control themselves--and it may be too late.