Cuando desaparece la esposa del agente del FBI Flynn Carroll, las pistas lo llevan a un oscuro grupo de terroristas internacionales conocidos como cazadores. Para encontrar a su esposa, Flynn se une fuerzas con la Unidad de Exo-Terrorismo (ETU), una división altamente clasificada de Seguridad Nacional encargado de detener a los cazadores y terroristas que ni siquiera pueden ser humanos.

Los cazadores están bombardeando objetivos al azar en suelo estadounidense y matando a civiles inocentes. Flynn y la ETU investigan los actos terroristas violentos, y descubre que los cazadores están trabajando con colaboradores humanos - que conduce Flynn a la pregunta ¿por qué secuestraron a su esposa?.

La ETU sigue el rastro de los cazadores hasta un campamento de drogas en la selva colombiana donde se enfrentan contra una nueva y peligrosa amenaza. Flynn tiene que aprender a confiar en su pareja, Regan, mientras se enfrenta a su propio pasado.

McCarthy is captured as Flynn's search for his wife leads to desperate actions. Plus: Get ready for a Hunter birth!

Flynn stumbles upon startling new information about his wife, which leads the ETU to a suspected human-hunter collaborator, while Flynn finds himself in an unexpected confrontation.

The ETU's discovery of the name and suspected location of a High Value Target, dredges up old memories for Jackson. Meanwhile, Flynn, Regan and Briggs attempt a daring raid on a Turkish prison.

The Hunters attempt to "reprogram" a captive Regan. While the ETU work to locate their missing agent, they deal with the possibility that there could be a mole in their ranks.

Regan discovers that she wasn't told the truth about her father's disappearance. Meanwhile, Flynn and Briggs race against the Hunters to acquire a scientist critical to "The Purge."

Flynn (Nathan Phillips) struggles with his self-destructive downward spiral, Regan (Britne Oldford) confronts her mother, and the Hunters make last-minute preparations for The Purge.

The ETU finally cracks the Hunter language, allowing Finnerman (Sarah Peirse) to set a trap. Regan (Britne Oldford) questions whether all Hunters are terrorists, or whether some may be innocents living among us.

In the fallout of the Hunter roundup, Jackson (Lewis Fitz-Gerald) and Finnerman (Sarah Peirse) are at odds with each other. The ETU's only hope of stopping The Purge is to make a risky move on the Hunter's weapons' supplier, Viktor Karp (Erroll Shand).

With The Purge imminent, the ETU has no choice but to trust an unlikely informant, leading all paths to converge at the primary Hunter base for a climactic showdown.