 A group of hikers are caught in a rainstorm and go into a cave for shelter. While in the cave they meet an archaeologist who is studying some of the paintings on the wall. The archaeologist then entertains the hikers with a story he has been able to interpret from the paintings. He tells the story of a young caveman named Tumak, the son of the chief of the uncivilized Rock Tribe, and Loana, the daughter of the chief of the more peaceful Shell Tribe. He tells of their struggles for survival and how the two tribes eventually became one.