WATCH ONLINE, MOBILE, FREEVIEW 64, SKY 164, SKY GLASS / SKY STREAM 169, FREESAT 162 AND VIRGIN 174
Alien Origins: The compelling series returns to examine more eerie reports of UFOs. Can it determine where in the universe such strange flying crafts could be coming from? (S2, ep 1)
Human Harvest: A look at frightening reports of alleged alien abduction, including cases in which abductees claim to have been subjected to torturous medical experiments. (S2, ep 2)
Astronaut Encounters: To this day, NASA denies all UFO accounts and has taken measures to prevent its astronauts from telling their stories. But what are they hiding? (S2, ep 3)
Atmospheric Anomalies: Some experts believe many atmospheric light shows are actually caused by extraterrestrials. If so, do they pose an imminent threat to humanity? (S2, ep 4)
Alien Apocalypse: If extraterrestrials visited Earth would they enlighten us or destroy us? Experts examine the possibility of a doomsday orchestrated by an alien enemy. (S2, ep 5)
Top Ten Military Encounters: A fascinating and shocking countdown of the top ten military encounters between Earth's armed forces and UFOs. (S2, ep 6)
Alien Skies: From mid-air abductions to near-disasters caused by unseen enemies, experts examine if we are alone in the skies over Earth. (S2, ep 7)
The Next Wave: A fascinating look at the mounting evidence that suggests UFO waves are able to penetrate the world's most closely guarded airspace at will. (S2, ep 8)
Signs of Abduction: From loss of time and bizarre hazy memories, to terrifying accounts of alien surgery, these are the hidden signs of alien abduction. (S2, ep 9)
Antigravity: Experts discuss the possibility of advanced alien technology that could allow UFOs to fly at blinding speed or hover effortlessly a few feet above the ground. (S2, ep 10)
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)
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)
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)
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)
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)
Alien Bodies: Uncover the shocking truth about alien remains as experts investigate unsettling reports of extraterrestrial bodies recovered from crashed UFOs. (S2, ep 16)
UFO Zones: Journey to the world's hottest UFO zones, where physical and paranormal phenomenons and unidentified objects and aliens are reported with alarming frequency. (S2, ep 17)
Countdown To Disclosure: Evidence suggests the world's governments could be on the verge of announcing everything they know about UFOs. What will this mean for our society? (S2, ep 18)
Top Civilian Encounters: From mass sightings in the sky to reports of alien probes found in human bodies, explore the ten most disturbing extraterrestrial encounters ever. (S2, ep 19)
Alien Achilles Heel. Many believe aliens are already here on Earth. Could they be plotting an attack? And if so, can humans survive their weapons' terrifying capabilities? (S2, ep 20)
Second Skin: To enter space, humans require a space suit. Are the aliens that are said to have visited earth any different? Or are they more akin to artificial drones? (S4, ep 1)
The 1952 Wave: In Spring 1952, reports of UFO sightings shot through the roof. Can former US Air Officials shed any light on this? (S4, ep 2)
The Freedom of Information Act: In 1969, the US government officially announced it would stop investigating UFOs, but declassified documents seem to tell another story. (S4, ep 3)
The Shoot Down Order: Jets are scrambled to intercept a UFO, but find they are unable to complete their Shoot Down Order. (S4, ep 5)
Seeing is Believing: For decades, governments around the world have investigated UFO sightings. How are these top-secret studies conducted? (S4, ep 6)
Inside UFOs: Those who claim to have been abducted by extraterrestrials give their accounts of the interior of their spacecrafts. (S4, ep 7)
Unwelcome Visitors: If aliens have visited Earth, what are their intentions? Do they wish to experiment on the human body, or the human mind as well? (S4, ep 8)
Alien Journeys: Alien encounters have offered a possible glimpse into the secrets of interstellar navigation. Could this one day ensure mankind's survival? (S4, ep 9)
Finding Aliens: Advances in technology have given us unprecedented access to distant galaxies that may harbour life. However, alien life may be found closer to home. (S4, ep 10)
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)
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)
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)
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)
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.
Mass Sightings: While many UFO sightings occur in rural locations with only a single eyewitness, there have been sightings over cities witnessed by hundreds. (S4, ep 16)
Mars: The New Frontier: With science closer than ever to proving that life once lived on Mars, is there a chance that something still exists there? (S4, ep 17)
Alien Communications: With light from distant stars taking millions of years to reach us, how long might it take for alien life to answer any communication sent into space? (S4, ep 18)
Artificial Alien Intelligence: Is biological life merely a stepping stone for a universe dominated by alien artificial intelligence? (S4, ep 19)
First Contact: As humanity continues to search for alien life, experts give their analysis on how close we are to First Contact. (S4, ep 20)
Series investigating compelling UFO and alien cases by opening previously off-limits secret files. Does the mysterious Blue Planet Project hold the answers? (S1, ep 1)
Recently-declassified FBI files cast new light on the existence of aliens, as well as question whether the Vatican could be hiding proof of extra-terrestrial life. (S1, ep 2)
Experts investigate why so many UFO sightings take place in Los Angeles, determining that the answer may lie underwater. (S1, ep 3)
Previously sealed documents hint at compelling new theories about extraterrestrials. Could aliens be living among us? And could former US Presidents know something we don't? (S1, ep 4)
A look at the possibility that life began on Mars and travelled to Earth. Plus, if aliens exist, what plans do they have in store for us? Experts investigate. (S1, ep 5)
Experts open previously off-limits files in a bid to answer some of the most mysterious questions surrounding UFOs and extra-terrestrial life. (S1, ep 6)
Experts open previously off-limits files in a bid to answer some of the most mysterious questions surrounding UFOs and extra-terrestrial life. (S1, ep 7)
Top Ten Countdown: An out-of-this-world look at ten of the most fascinating alien encounters ever. (S1, ep 8)
Experts investigate evidence suggesting that aliens have created the means for controlling humanity. They find that the shocking truth might be hidden right inside you. (S1, ep 9)
Could Hitler's crazed quest for world domination have been influenced by aliens? Experts reveal the extraterrestrial secret Hitler may have been hiding and where it is now. (S1, ep 10)
Experts unseal the truth about the potential aliens living and working among us. Who has come in peace? And who has a more sinister motive in mind? (S1, ep 11)
The Solway Firth Spaceman: Experts investigate the mystery of the Solway Firth Spaceman - a spacesuit-clad figure who strangely appeared in a photograph taken in Cumbria . (S1, ep 12)
Aliens and Presidents: Could history's most powerful men know more about extra-terrestrials than us? Experts explore the complex relationship between presidents and aliens. (S1, ep 13)
Alien Gods of Egypt. Experts scrutinise the engineering behind the Egyptians' Sphinx and pyramids. Could this advanced civilisation have received extra-terrestrial help? (S1, ep 14)