Space Shuttle Encounters: Between 1981 and 2011, cameras on NASA space shuttles have picked up many images of UFOs that experts still struggle to explain.

Nazi UFOs: Could alien technology have helped the Nazis' rise to power? Experts question whether Hitler had extraterrestrial help in his quest for world domination. (S2, ep 15)

Police Sightings: For many people, the most credible UFO reports are those raised by law enforcement. We investigate the most significant reports from police records. (S4, ep 14)

Solar System UFOs: Discover the shocking truth about alien civilisations in our solar system. Check out derelict spacecrafts and explore the mysterious origins of UFOs. (S2, ep 14)

Summer of Saucers: In 1947, there was an unprecedented wave of UFO sightings that propelled the UFO phenomenon to the world stage. What were the US Air Force's findings? (S4, ep 13)

Earth Portals: Experts unravel the secrets of the universe's earth portals: shortcuts through space that allow travellers to span vast distances in the blink of an eye. (S2, ep 13)

UFOs from Earth: For years many have argued that UFOs are as terrestrial as you or I. They may be correct, but not in the way they thought they were. (S4, ep 12)

Triangle Terror: For years, the flying saucer has been synonymous with UFO terror. But is it still the spacecraft that frightens us the most? Or has fear taken a new shape? (S2, ep 12)

UFO Photos: As the world continues to evolve into the digital age, more and more people are capturing images in the sky that they are unable to explain. (S4, ep 11)

UFO Metal: Nations all over the world are rumoured to have found metal debris from UFO crashes. Join the investigation into the alleged wreckages of otherworldly crafts. (S2, ep 11)