If ancient aliens visited Earth, who were they, and where did they come from? Possible historic evidence and beliefs are examined around the world. The Dogon people possess knowledge of a galaxy they claim was given to them by a star god named Amma. The Hopi and Zuni people celebrate Kachinas, gods from the sky, whose headdresses and costumes appear to resemble modern helmets and protective clothing. Halfway around the world, Chinese legends tell of the Han leader, Huangdi, arriving on Earth on a flying, yellow dragon. Was this dragon more likely a spacecraft? Ancient astronaut theorists believe that these are far from chance encounters and that extraterrestrials not only interacted with us, but changed the course of human history.

Reports of encounters with strange beings and sightings of mysterious objects in the sky have occurred throughout history. A 13th century historical book, Otia Imperialia, includes an account of a creature descending from a flying craft over Bristol, England. The log from Christopher Columbus' first voyage to America contains a report of strange lights in the sky. Medieval art pieces depict disc-shaped objects floating in the heavens. Sightings of flying cigar-shaped crafts were reported during the Black Plague. And there were even discussions of extraterrestrial life among America's Founding Fathers. Could these sightings, coming from every part of the world, from biblical times to present day, be evidence that aliens have been with us all along?