A young boy while walking though a grassy field falls down a hole in the ground and into a cave. After the town's sheriff checks the cave, an archaeologist, Dr. Klein, is called to investigate things more deeply.
Dr. Klein recognizes paintings inside the cave as original primitive drawings and thinks that the site needs further researching. Opposing her is a landowner who wants her out of there so he can finish building some houses before he goes broke. Dr. Klein thinks he is threatening her because a sheep's carcass was found close to the cave's entrance.
Other strange things start to happen: More sheep disappear and the sheriff finds blood trails leading to the cave. Stranger still, Dr. Klein discovers that the hunters in the paintings on the walls change positions every night. When she shows this finding to the sheriff, he tells her to take a break and come back later. She refuses and decides to stay overnight in the cave so she can find the person who is messing with the paintings.
Dr. Klein is woken by strange sounds early in the morning. She notices that all the hunters from the paintings are gone now and that strange noises are surrounding her. Suddenly, the sheriff, who spent the night outside in his jeep, is woken up by a loud scream from inside the cave. He enters and finds Dr. Klein dead on the floor with a spear in her back. Whatever killed Dr. Klein is lurking in the dark and the sheriff knows it. He empties his revolver trying to hit some shadows around him. Moments later, the sheriff notices that Dr. Klein's body has disappeared but he is more confused when he sees the hunters in the paintings dragging a speared corpse from one place to another.
Noise from the other end of the cave warns the sheriff that something is coming his way so he decides to end this game in an unusual way. Water and brush in hand he starts to scrub away the hunters in the paintings and as he is doing it a hunter who is about to spear him in the back disappears instantly.