An alien spaceship crash-lands in an isolated town in the middle of the Australian desert, releasing an insidious parasite that attacks the brain of all creatures including humans, making them disorientated, unnaturally strong and violent. Sargeant Jo Sharp, readying for a return to the big city beat, wakes to find the township, her family and friends falling victim to an evil that is spreading faster than it can be contained.

In 1825, Claire, a 21-year-old Irish convict, chases a British soldier through the rugged Tasmanian wilderness, bent on revenge for a terrible act of violence he committed against her family. She enlists the services of an Aboriginal tracker named Billy, who is also marked by trauma from his own violence-filled past.