The team heads to Sonora, Calif., to explore whether sightings of triangular ships are indeed UFOs or attributable to military aircraft; the team builds a model of a triangular UFO based on an ancient artifact found in Colombia.
Stories about a massive UFO coverup, cattle mutilations, a shootout with aliens and a secret underground base have made Dulce, N.M., a mecca for UFO enthusiasts.
People recount their stories of encounters with grey aliens; an astrobiologist analyzes artist renditions of greys to try to determine what planets the creatures might inhabit; 900-year-old skull found in Mexico.
Satellite images show what appear to be underwater landing strips and other strange evidence in the wake of UFO sightings in Gulf Breeze, Fla., and reports from Cuba reveal unidentified submerged objects rising from the ocean.
The team travels to Germany and Poland to investigate bizarre, centuries-old alien links that might be connected to technology unleashed by Nazi Germany during World War II.
The team analyzes the phenomenon of cows being slaughtered in the same strange and meticulous way around the world for the past four decades.
Investigating reports of a UFO spraying a strange blue mist in Pennsylvania; examining what are said to be UFO relics from the United States and Poland.
Investigating reports of UFO and USO activity in the Bermuda Triangle vicinity of the Atlantic Undersea Test and Evaluation Center said to be used by the U.S. Navy for weapons testing and underwater research.
The team investigates videos indicating a strong UFO surveillance presence at weapons laboratories.
A growing phenomenon involves purported sightings of UFOs known as orbs, whose witnesses report experiencing odd dreams, premonitions and deep fear; the team investigates orb sightings in Arizona, Indiana and Missouri.
The team tries to uncover U.S. military forces' first responses to UFO encounters; investigating a claim that military helicopters pursued UFOs over Long Beach, Calif.; revisiting a suspected UFO crash site in Needles, Calif.
UFO watchers report strange phenomena at a remote military site in Utah; bizarre beams of light; an astrophysicist charts mysterious cosmic rays.
People driving home from an Ozzy Osbourne concert in Tingley Park, Ill., on Aug. 21, 2004, report seeing a large, triangular UFO with three bright red lights with more sightings happening on the following Halloween in suburban Chicago.
Investigating strange airborne lights filmed over Denver; an ear-piercing, high-decibel boom accompanied by sightings of orange balls of light in the sky rocks Kokomo, Ind., April 16, 2008.
Investigators reopen a sealed well said to be the grave of an alien killed in a UFO crash reported in Texas in 1897.
The team investigates a report that there might have been a second "flying disk" crash at Roswell, N.M., that might finally reveal what really happened there in 1947.
James Fox, the filmmaker behind the UFO documentary "Out of the Blue," joins the team to investigate whether strange lights first reported in 1997 have returned to the sky over Arizona.
The team examines UFO files that have laid dormant in university archives since the tragic death of physicist James McDonald, whose groundbreaking investigatory work changed the course of UFO research.
The team investigates claims of "alien effects" to determine whether UFOs are leaving more behind than just sightings; a family from Texas attributes their horrible physical symptoms to a 1980 UFO encounter.
Former British Ministry of Defence investigator Nick Pope joins the team to probe a flurry of U.K. UFO sightings that erupted in June 2008.
The team probes some of the largest UFO sightings ever recorded; people aboard an airliner en route to London report seeing a flying disc as much as 1,000 feet long; mile-wide objects are spotted above the English Channel.
The team probes why UFOs are following aircraft and surveying airports; a strange object hovers over Chicago's O'Hare International Airport in 2006; a UFO is spotted tailing an airliner landing in Japan in 2004.
The team visits a California site where witnesses reported seeing a UFO crash, then military helicopters carrying away a glowing object in May 2008; the team tries to determine if the government is covering up the incident.
The team heads to Area 51, the epicenter of UFO and military conspiracy theories, to visit new vantage points, talk with former employees and search the skies above America's most top secret facility.
An Air Force team is in a deadly plane crash after investigating a Washington state UFO sighting reported a week before an incident in 1947 Roswell, N.M.
Bill Birnes, Ted Acworth and Pat Uskert investigate UFO cases around the world.
A purported alien abduction survivor undergoes surgery to have an implant removed for study by scientists trying to determine its origin and composition.
Coinciding crashes of a UFO and a civilian aircraft in 1974 Mexico and the ambush of a military convoy; 2007 reports of debris falling from the sky in Mexico.
Investigating reports of encounters between UFOs and the military; 1980 Rendlesham Forest incident in England; RAF incident in 1956.
Police officers tell of their own, unbelievable but substantiated, encounters with UFOs.
The team investigates reports that wreckage from UFO crashes has been used for reverse engineering.
Researchers investigate theories about the existence of UFO gateways in New York's Hudson Valley and the Arizona desert.
The team finds people who tell of having contact with aliens, then works with doctors and scientists to discover what happened to them.
The team conducts interviews and analyzes video footage shot after strange lights began appearing in the skies over Texas in December 2007.
Jet fighter pilots from Peru and Iran provide accounts of encounters with UFOs.
The team analyzes NASA footage of reported UFOs and alien presence.