Five friends and anja join anthroplogy student, Dace, on a journey to study a more remote stone painting. Their enthusiasm fades when Mel becomes delirious after skinny-dipping from the waterhole. Feverish, bleeding, perplexed, and she regresses to your predatory state and physically. Mel went primal. Friends and mel's enthusiast realize they're the prey as she cruelly hunts down them. Before they are able to escape the following one of these starts to babble, posing a hideous option. Kill their buddies or be murdered by these. Their sole hope of success is through a cave, even where Anja learns that the significance of the ancient stone art they came into review.