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.
Did a biblical patriarch receive instructions from 200 angels, and was Egypt's most controversial Pharaoh an extraterrestrial being? (S16, ep 1)
Ancient astronaut theorist Giorgio Tsoukalos takes a look back at some of the most mysterious yet incredible creatures ever investigated. (S16, ep 2)
Discover 10 locations around the world that just might be hiding alien bases, from a cavern beneath the ice in Antarctica to a Chinese lake. (S16, ep 3)
From a meeting in Texas that left onlookers with mysterious injuries to strange cattle mutilations, discover history's terrifying encounters. (S16, ep 4)
From glyphs in the Peruvian desert to spiral petroglyphs embedded with advanced maths, explore some of the world's most intriguing symbols and codes. (S16, ep 5)
Explore the most devastating disasters ever documented that may have an otherworldly connection, from a flying monster to a deadly virus. (S16, ep 6)
When the ancient Sumerians built their civilisation, they credited their gods - but were these powerful beings actually extraterrestrial visitors? (S16, ep 7)
With so many strange reports of UFOs, animal mutilations and more, a specific latitude north of the Earth's equator has been dubbed 'the UFO Superhighway'. (S16, ep 8)
Home to mysterious stone circles, stories of strange beings and reported sightings, Scotland has always been an epicentre of otherworldly phenomena. (S16, ep 8)
Mysterious ancient stones shaped into perfect spheres exist around the world - but can they provide clues about humankind's past? (S16, ep 10)
One of the greatest civilisations in the history of the Americas, the Maya thrived for over 2,000 years - but new evidence blurs our understanding. (S16, ep 11)
For centuries, cultures around the world have believed in stargates through which beings have travelled to Earth - but could such portals truly exist? (S16, ep 12)
For decades, claims of extraterrestrial presence on Earth have been made - and the government have gone to great lengths to discredit them. (S16, ep 13)
The Search for ET Intelligence: For thousands of years, humankind has attempted to make contact with extraterrestrial beings from beyond Earth. (S16, ep 14)
Throughout ancient cultures there are tales of god-like beings helping our ancestors to build civilisations and teaching them in various disciplines. (S16, ep 16)
Jacques Vallée - Pioneer of the Multiverse: Dr Jacques Vallée is best known for his work in the field of UFOs - and his bold theories challenge the notions of alien life. (S16, ep 15)
Deep beneath the sands of Egypt lie 24 enormous, empty sarcophagi - but what purpose might these giant tombs have served? And are they even man-made? (S16, ep 17)
For over 40 years, award-winning journalist Linda Moulton Howe has covered mysterious phenomena - which could lead us to a profound new reality. (S16, ep 18)
From biblical patriarchs to modern day alien abductees, throughout history, there have been people who claimed to have contact with otherworldly beings. (S16, ep 19)
Puma Punku in Bolivia features some of the largest stone blocks on Earth, each carved with incredible precision. (S16, ep 20)