First Response: The team attempts to uncover the US military's first responses to UFO encounters, leading them to revisit a suspected UFO crash site in California. (S3, ep 12)

Alien Crashes: In 2008, witnesses saw military helicopters carry away a glowing object. What was the government trying to hide? And could UFO clean-ups be common? (S2, ep 12)

Dark Presence: The team investigates growing numbers of flying orbs sightings, with witnesses also experiencing odd dreams, premonitions and deep fear. (S3, ep 11)

Aliens at the Airport: The team investigate a strange object seen over Chicago's O'Hare Airport in 2006. Are aliens watching our airports? (S2, ep 11)

Military vs. UFOs: The team examine incidents of alleged conflicts between the US Air Force and the RAF, and asking whether these encounters have been covered up. (S1, ep 11)

Area 52: Area 51 is considered the ultimate top secret facility, but there is another military site, known as Area 52, where strange phenomena have been witnessed for 10 years. (S3, ep 10)

Giant UFOs: The team probes some of the largest sightings of alleged UFOs ever recorded over the English Channel, including two eerie objects spotted by pilots in 2007. (S2, ep 10)

The NASA Files: The team analyses incredible NASA footage of reported UFOs, and interviews former NASA employees who allegedly witnessed cover ups first hand. (S1, ep 10)

The Silencers: UFOs are the biggest mystery of our time and somebody - or something - seems determined to keep it that way. (S3, ep 9)

UFO Storm: In 2008, the UK's Ministry of Defence released decades' worth of classified UFO files to the public. One month later, UFO hysteria ripped through the country. (S2, ep 9)