The series is a thorough examination of the infamous UFO cult through the eyes of its former members and loved ones. What started in 1975 with the disappearance of 20 people from a small town in Oregon, ended in 1997 with the largest suicide on US soil and changed the face of modern new age religion forever.
In the first episode, Bonnie Nettles and Marshall Applewhite begin to recruit individuals interested in end-of-the-world Christianity, new age religion, and UFOs - but the disappearance of new members soon drives media attention and family concerns.

From unexplained flashes in the night sky to flying saucers, this episode delves into the mysterious world of UFOs. How our drive to explain these bizarre phenomena, and desire to discover little green men, has in fact transformed our understanding of the universe

The Nazca Lines of Peru have been an important part of the Ancient Astronaut theory since its beginning. Originally Von Daniken claimed that the lines were kind of a UFO runway, or a type of alien airport, where the alien craft landed and took off. The idea that it was an airport makes no logical sense, and the symbols and rituals which were a huge part of the Nazcan culture more than explain the so called Nazca lines.

Questions are raised about the search for intelligent life beyond the Earth, with UFOs and other close encounters refuted in favor of communications through SETI and radio telescope such as the Arecibo Observatory. The probability of technically advanced civilizations existing elsewhere in the Milky Way is interpreted using the Drake equation and a future hypothetical Encyclopedia Galactica is discussed as a repository of information about other worlds in the galaxy. The Cosmos Update notes that there have been fewer sightings of UFOs and more stories of abductions, while mentioning the META scanning the skies for signals.

What sort of alien civilizations might exist in the vastness of space? Terra is the fictional world imagined in Episode 4, a planet nine billion years old, twice as old as Earth. Old enough that a truly advanced intelligence could evolve. It was once a fertile world, now it is barren. But life can still thrive here in artificial domes. Over time, they've evolved not to need their bodies. They exist only as neural tissue. They never age, they never die. They're monitored and maintained by robots.
If alien civilizations are statistically so likely, why haven't astronomers found any sign of them? Where is everyone? Every time we look at an individual star, that's like dropping a bucket in the ocean. We're going to have to look at a lot of stars and to search through a lot of data until we find the clue that leads us to another civilization.

Bonnie and Marshall - 'Ti' and 'Do' turn to recording their lessons to teach their followers how to transcend, and the intense rule and check partner system is set-up. The renaming of the members, the haircuts, and the clothing style also are changed to fit an androgynous look.
When Ti is given a cancer diagnosis, the dynamic of the group changes. After Ti dies from cancer in 1985, a distraught Do briefly allows members to visit their families. When the members return, Do becomes more controlling.