There's no turning back. . . . For Cassie and her Circle of witches, it's hard to imagine life in New Salem getting any worse. A band of powerful witch hunters is targeting the group, determined to destroy them one by one. And Cassie's half sister, Scarlett, won't rest until she has a spot in the Circle—even if she has to kill Cassie to get it. The Circle's only hope against their enemies is Cassie's father's Book of Shadows—an ancient guide to the world of dark magic. But Cassie soon discovers that opening the book has grave consequences. Cassie's drawn in by the book's sinister spell, and it starts controlling her emotions and impulses, unraveling her relationship with Adam as it takes over her life. Cassie fights against the darkness inside her as the threats against the Circle grow. But once evil is let in, she may never escape. . . .