Green’s debut novel is set in modern-day England where witches live alongside humans. Due to his mixed parentage, 16-year-old Nathan Byrn is labeled a Half Code. His father is the powerful and cruel Black witch Marcus, and his mother, a White witch, is dead. Trapped in a cage, Nathan is beaten regularly and must escape before his seventeenth birthday or else he will die. Both the black and white witches want Nathan to kill Marcus, but he has no desire to kill anyone and only wants to escape and gain his freedom. But how can Nathan find his father when his every action is tracked and he can't trust anyone, not even the girl he loves?