FBI agent Flynn Carroll is a former soldier who suffers from PTSD following a tour in Afghanistan and depends on wife Abby to help save him from himself. When Abby goes missing, Flynn's search for her leads him to the discovery of a classified government organization, the Exo-Terrorism Unit, which fights alien terrorists known as Hunters. Recruited by the ETU, Flynn works with Allison Regan, the agency's most valuable operative, who harbours a secret that may hold the key to why she is so good at tracking down Hunters. The sci-fi drama is inspired by Whitley Strieber's novel `Alien Hunter'.