The theory that extraterrestrial visitors shaped ancient civilizations gets its television treatment here, narrated by Rod Serling and produced by Alan Landsburg as one of the earliest In Search Of... specials, itself edited down from the 1970 German film Erinnerungen an die Zukunft (Chariots of the Gods). The film moves site to site: the pyramids of Egypt, the Nazca Lines in Peru, the monolithic statues of Easter Island, and Bolivia's Tiahuanaco ruin, where the carved Gateway of the Sun becomes a centerpiece. Researchers cited in the film, including Charles Berlitz and Erich von Däniken's line of argument, point to the gateway's mathematical precision, angles reportedly accurate to within 1/50th of an inch, as evidence the structure exceeds what its builders could have achieved unaided. Conventional explanations get airtime too, including the theory that pre-Inca laborers moved the stones through sheer numbers and organized labor under religious and royal authority. The film presents its case through artifacts, ruins, and narration rather than argument for argument's sake, leaving the comparison between the two explanations to the viewer.