Heartland Explosion: The team finds new evidence concerning the strange booms and orange lights that panicked Indiana in 2008, disbanding theories it was a military jet. (S2, ep 2)

USOs: The team use high-tech sidescan sonar and deep sea magnetometers to search for evidence after learning of an encounter with an underwater phenomenon. (S1, ep 2)

Giant Triangles: The team uncovers rare footage of floating giant triangles hovering over cities. Could these strange sightings be extraterrestrial in origin? (S3, ep 1)

Invasion Illinois: Series examining UFO sightings, alien abductions and government cover-ups, beginning with an investigation into multiple sightings in Illinois in 2004. (S2, ep 1)

Cops vs UFOs: Hear first-hand accounts from seasoned, decorated police officers who have had unbelievable, but substantiated UFO encounters. (S1, ep 1)

Russian Roswell: An exploration of the facts and myths surrounding the Soviet-era UFO research programmes at Kapustin Yar. (S1, ep 16)

Real UFOs: A look at the secret flying saucers designed by the military around the world. Sightings in the US, South Africa, Russia, Australia and Canada have all given the locals a fright.

Mexico's Roswell: In 1974, the US government was tracking a UFO when it disappeared over Coyame, Mexico. At the same time, a civilian plane crashed. Why was it all covered up? (S1, ep 14)

Britain's Roswell: In December 1980, Air Force personnel witnessed strange lights hovering above the English countryside. Did they have a close encounter with alien spacecraft? (S1, ep 13)

Brazil's Roswell: In 1977, a remote Brazilian island was visited nightly by strange flying objects, leaving people with bizarre puncture marks and blood loss. What happened? (S1, ep 12)