Anja, Mel and four friends join anthropology student. Dace, on a journey to study a remote, ancient rock painting. Their excitement vanishes when Mel becomes delirious after skinny-dipping in a water hole. Feverish, bleeding, confused, she physically and mentally regresses into a vicious predatory state. Mel has gone primal. Mel's lover and friends realise they are the prey as she savagely hunts them down. Their only hope of survival is to escape through a cave, where Anja learns too late the dark meaning of the rock art they came to study.