UFO sightings don't just come from crackpots: in 2004, a team of elite Navy pilots and radar operators had one of many military encounters with unidentified aerial phenomena. As evidence mounts, the government, along with alien-obsessed billionaire Robert Bigelow, grow more interested in UFOs and the paranormal — and the conversation around them moves from the fringes to the center of the Pentagon.

Even as the New York Times brought credibility and a broad audience to the question of UFOs and extraterrestrial life, other figures challenged whether it might all be a great big lie. But when an acclaimed Harvard psychiatrist named John Mack began investigating the phenomenon now known as alien abductions, he proved that these bizarre experiences couldn't be so eagerly dismissed — and that the truth might be far more complicated than we imagine. Series finale.