When Harvard student Emma Hale disappears, her father believes she has been kidnapped. Months pass and the trail goes cold but then her body is found floating in Boston Harbour. A year later, Judith Chen, another student, disappears. Like Emma, she is soon found dead in the river. CSI Darby McCormick is assigned to the case and uncovers a key piece of overlooked evidence, one that brings her into contact with Malcolm Fletcher . . . a former profiler, now on the FBI's Most Wanted list. Fletcher, it seems, not only knows the answers but also the identity of the killer. When a third student goes missing, Darby is led into a dangerous game of cat-and-mouse with the former profiler . . .