The astronauts Mac McKenzie and Hector Canfield travel faster than the speed of light, and then accidentally travel back to planet Earth's prehistoric past, in the Stone Age. They find hospitality from a nuclear family of cavemen consisting of the father Gronk, the mother Shag (or Shad), the young adult daughter Mlor, and the adolescent son Breer. After several episodes of trying to modernize the local tribe, the astronauts manage to repair their space capsule and return to the year 1967. But they take their new surrogate family with them. The cavemen have to adapt to living in 20th-century Los Angeles.