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.
Rumours are rife that aliens inhabit the continent of Antarctica, but is it true? This episode explores the icy wilderness to find out. (S12, ep 1)
The series investigates satellite images of what seems to be a giant face carved into the earth in Alberta. Could this have extraterrestrial origins? (S12, ep 2)
Physicist Bob Lazar says he was hired to reverse-engineer an alien spacecraft by the US government, with a fuel source that had the power to change the world. (S12, ep 3)
Experts investigate whether aliens from a tiny star visited humans in the past, and left behind a clue that still remains in our language. (S12, ep 4)
From octopuses that can edit their DNA to jellyfish that can live forever, were the unusual creatures of our oceans delivered to Earth by aliens? (S12, ep 5)
When Spanish Conquistadors obliterated the Mayan people's history, could they have erased proof of extraterrestrial visitors? Experts investigate. (S12, ep 6)
Experts examine strange stone structures on New England and New York's landscapes. Could they be clues of alien visitors to Earth? (S12, ep 7)
The Reptillian Agenda: Serpent gods are found in many religious texts. Could these stories be describing reptile-like extraterrestrials? And are they still here today? (S12, ep 8)
Is our planet prepared for an extraterrestrial invasion of disease? And could past plagues have been brought to Earth by aliens? Experts investigate. (S12, ep 9)
Experts explore animal mutilations and alien abductions as they ask whether extraterrestrials could be altering human DNA. (S12, ep 10)
Could ghosts and angels be visitors from other-worldly realms? A team of ancient alien theorists explores. (S12, ep 11)
Could Hawaii's islands have once been inhabited by extraterrestrials? Experts investigate whether its volcanoes provide a portal between space and time. (S12, ep 12)
Experts check out structures built to mirror the constellations. Could they have been built as a message to extraterrestrials? (S12, ep 13)
Nuclear Agenda: Ever since the first atomic bomb went off in 1945, UFOs have been spotted at nuclear facilities across the world. Could this signal a threat to mankind? (S12, ep 14)
Experts investigate an Italian mountain that's stood witness to inexplicable phenomena for centuries. Could it somehow be attracting alien visitors? (S12, ep 15)
Telepathy: Could aliens have given our brains incredible untapped abilities? Experts ask whether harnessing these hidden powers could spark the next step in our evolution. (S12, ep 17)
A DNA study released in 2018 revealed that the original builders of Stonehenge mysteriously vanished - did they head back to a home among the stars? (S12, ep 16)
Experts question the link between divine substances and extraterrestrials. Could the food of the gods really have been sustaining Earth's alien visitors? (S12, ep 18)
Tattoos, piercings and body modifications are big business. But could our desire for these changes stem from a profound link to our ancestors? (S12, ep 19)
When millions responded to a call to storm Area 51, the US military vowed deadly force. Are they hiding the truth about extraterrestrials on Earth? (S12, ep 20)
Over the past 20 years, thousands of potentially habitable exoplanets have been found. Could they be home to intelligent extraterrestrial life? (S12, ep 22)