Renowned FBI profiler Karen Vail returns in an explosive thriller set against the backdrop of California's wine country. Seeking a romantic respite with her boyfriend, Vail ventures to Napa Valley. After arriving, Vail learns a serial killer is crushing his victims' windpipes and leaving their bodies in caves. When the Crush Killer learns that an FBI profiler has joined the Major Crimes Task Force, the newfound attention emboldens him, and he sets in motion a plan that wreaks havoc on the town and the task force. Vail is frustrated by her inability to profile the offender—until she realizes why: the Behavioral Analysis Unit has never before encountered a killer like him.