The inland ice has advanced a bit in Sweden, and animals and people are migrating down from Europe. The Hedenhös family is among the first. There is father Ben, mother Knota, daughter Flisa, and son Sten. They have brought along their primitive dog Urax, their cow Mura, and their toys. The Hedenhös family settles in Sweden, lives in caves, founds Stockholm, and travels to Egypt. The Hedenhös family discovers America, visits Native Americans, flies through the air in the world's first atomic-powered aircraft, and returns to Sweden again.