Norwegian adventurer Thor Heyerdahl (Pål Sverre Hagen) suspects that the South Sea Islands were originally colonized by South Americans. In 1947 despite his fear of water and inability to swim, Heyerdahl decides to prove his theory. He and five companions set sail from Peru on a balsa-wood raft built from an ancient design. Their only modern equipment is a radio, and they must navigate using the stars and ocean currents. After three exhausting months at sea, they achieve their goal.