Ellie Linton (Caitlin Stasey), a teen from an Australian coastal town, leads her friends (Rachel Hurd-Wood, Lincoln Lewis) on an excursion to a camp deep in the woods, dubbed Hell. Upon their return, the youths find that their town has been overrun by an enemy army, and their friends and family have been imprisoned. When the hostile invaders become alerted to their presence, Ellie and her friends band together to escape -- and strike back against -- this mysterious enemy.