Investigators search for clues, regarding potential alien visits to Earth, contained in Indian Sanskrit texts, Jewish Zohar writings, and megalithic Egyptian stone structures.

Investigating possible historic evidence and beliefs around the globe in search of signs that aliens visited ancient Earth; Hopi and Zuni Indians celebrate Kachina sky gods; the Chinese legend of Huangdi arriving on Earth on a flying dragon.

Strange evidence in cultures throughout history indicates aliens came to Earth on missions to explore, obtain raw materials, experiment on humans and conquer; Sumerian tablets describe an alien race; Egyptian hieroglyphs depict hybrid creatures.

Alien encounters and UFO sightings have been reported throughout human history. As far back as the medieval period, disc-shaped objects were found depicted among the heavens in works of art.

Investigators take a look at the possibilities of alien contact in the 20th century, examining reports of a 1947 UFO crash in Roswell, New Mexico, as well as a 1942 aerial battle in the sky over Los Angeles.

From Mexico's mystifying Zone of Silence to Markawasi Plateau in Peru to the Bermuda Triangle, certain sites combine ancient clues of potential alien visitation with mysterious present-day UFO activity.