Dexter Harris, a marine biologist and devoted family man, comes home to find his wife and child murdered during a home invasion. He hopes for justice; however, his family's murderers are sentenced lightly. On the edge of a mental breakdown, he seeks the help of a psychologist, Dr. Miranda Miller, who diagnoses him with post-traumatic stress disorder. After only a couple of visits, Dr. Miller's therapeutic relationship with Dexter is on the verge of becoming compromised by Dexter's progressive mental instability. Dexter begins to mentally replace his deceased wife and child with Dr. Miller and her daughter. Finding out that Dr. Miller has a husband, Kevin Miller, infuriates Dexter and sets him on a path of destruction. Kidnapping and brutally murdering Raymond Tucker, his family's killer, he continues on this hunt and kidnaps Kevin. Suspecting that Dexter is responsible, she races against time to find Kevin before he becomes the next victim.