In this fourth book, Cassie and her fellow Naturals (teenage FBI profilers) close in on a generations-spanning society of sadistic serial murderers carrying out a dark ritual that may involve Cassie's missing mother. The web of crime the teens unravel is dense and complex, and each clue they discover is more chilling than the last. A compelling conclusion to a strong series.

Gr 9 Up-n this fourth volume of the series, Cassie Hobbs and her team of teenage FBI profilers are on the hunt for an organized group of serial killers. When people from their past investigations begin turning up dead, Cassie realizes that her team members are actually the prey. Soon, the very qualities that have made them such an effective team start to unravel them all. Cassie reads people by studying their behavior, personalities, and environment, but has blocked much of her own painful history after her mother's disappearance. Lia the lie detector puts herself in danger to get information from a cult; Michael the emotion reader goes head-to-head with his abusive father; Sloane the statistician digs deeper into logic and numbers to protect her grieving heart; and Dean the profiler has to face the possibility that he's more like his cold and calculating father than he ever knew. Initially, the narrative is stilted, relying heavily on exposition to get the story rolling, but once the unreasonably smug serial killer delivers his tip and is out of the way, the writing picks up significantly. Character motivation and the story's feinting twists become the driving force of this tightly plotted and gruesomely compelling thriller. Subplots and red herrings abound but converge logically, creating a satisfying and surprising conclusion with room for even more sequels. This volume can be read as a stand-alone for those immune to plot spoilers. VERDICT Recommend to fans of the series and to older teens who crave dark and fast-paced psychological thrillers in the style of Criminal Minds.Leighanne Law, Scriber Lake High School, WA