Investigators circle the globe in search of evidence in their quest to determine whether life on Earth began in outer space and if aliens influenced mankind in ancient times. Did extraterrestrial beings visit Earth and share information about technology and influence human religions? And more importantly, if aliens visited the planet before, will they return? Alien theorists believe that the answer to both questions is a resounding yes.
Ten archaeological finds, including mysterious spheres and a lost city, challenge our views on human origins and extraterrestrial links. (S17, ep 1)
Discover the top ten mysterious monoliths, from a 500-ton stone tied to UFOs to giant statues hinting at advanced tech and visitors. (S17, ep 2)
An acorn-shaped crash, a craft in Japan and a baffling impact in Britain - could these strange events prove Earth has been visited? (S17, ep 4)
Top ten Unexplained Technology: Explore 10 astonishing, unexplained technologies: from golden orbs in Mexico to a sacred box said to speak with the heavens. (S17, ep 5)
Secret agents, silenced UFO witnesses and hidden tech programs - could these mysterious projects prove contact with extraterrestrials? (S17, ep 3)
From Sri Lanka's mystical portal to Washington's volcanic encounter, these peaks spark questions about possible alien connections. (S17, ep 6)
The Aztecs built one of the world's most powerful empires and they claimed that they were guided by a pantheon of more than a thousand Gods. (S17, ep 7)
Luminous spheres are appearing globally, moving oddly near military sites, sparking speculation about extraterrestrial contact. (S17, ep 8)
The Legacy of J Allen Hynek: Was Dr Hynek right when he ultimately concluded that there is a non-human intelligence on Earth? (S17, ep 9)
The connection between volcanoes, myths and UFO sightings, suggesting that they might attract extra-terrestrial visitors due to their unique energy. (S17, ep 10)
Throughout the ancient world, there are depictions of mysterious figures that appear to be half-human and half-bird. (S17, ep 11)
People claim they have been abducted by aliens. A number of researchers have dedicated their lives to uncovering what is behind this disturbing phenomenon. (S17, ep 12)
Exploring how some archaeologists claim to have found skeletons of extraordinary size. Is it possible the giants actually existed? (S17, ep 13)
In the age of smartphones and social media, more evidence of otherworldly activity has come to light than ever before. (S17, ep 14)
Could it be that these mythological tales are based on real encounters with extraterrestrial beings? (S17, ep 16)
Japan has long been a place of wonder. Delve into the age-old mysteries, examining how they connect with the recent surge in UFO activity. (S17, ep 17)