Whilst on a camping weekend a young couple are carjacked by an escaped criminal and his crazed girlfriend. As the foursome head deeper into the wilderness, they are targeted by a blood-hungry parasitic creature that absorbs the corpses of its victims. Seeking shelter at an abandoned petrol station the insatiable parasite begins taking over them one by one and with no means of telling who's been infected and who can be trusted, the possibility of escaping alive is increasingly remote.