Five friends and anja join student on a travel to study a remote stone painting. Their excitement disappears when Mel becomes delirious after skinny-dipping from the waterhole. Bleeding, feverish, perplexed, and she emotionally regresses to some barbarous predatory state and physically. Mel went undercover. Friends and mel's enthusiast realise they are the prey because they are savagely hunted by her down. Before they could escape the following among these starts to regress, posing a choice that is horrible. Kill their buddies or be murdered by these. Their only hope of survival is via a cave, by which Anja learns the meaning of the early stone art they came into study.