Sir David Attenborough chooses his favorite recordings from the natural world --from the song of the largest lemur to the song of the humpback whale to the song of the lyrebird-- that have revolutionized our understanding of song. The science of song had been transformed by Charles Darwin’s theory of sexual selection: singing is dangerous as it reveals the singer’s location to predators, but it also offers the male a huge reward, the chance to attract a female and pass on genes to the next generation. Today, new science in the field of birdsong is transforming those long-held ideas.
Scientists are discovering that, in fact, in the majority of all songbird species, females sing - and it is only now they are being properly heard. Through this revelation and others, we can understand that animal songs are marvellous examples of the spectacular survival strategies that species have developed.

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.

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.

The message of the group begins to change and losing identity and group mentality is pushed. With more lockdowns and rules, longtime members of the group begin to question or leave. With no sex permitted with members, Dick Joslyn’s membership in the cult poses problem for Do... leading to a new request for the group.
With dwindling numbers, the group needs a new boost of membership. The Exit begins to be discussed as the Hale-Bopp Comet approaches.

Feast your eyes on a reconstruction of the mega-city and its amazing buildings. Alexandria, built in the middle of rancid marshland, had become in less than a century, the greatest city of the Mediterranean. An ideal position at the crossroads of east and west, and one that brought her great riches. Huge, modern, gleaming white and cosmopolitan, like no other in antiquity, it created its own identity.
While the beauty of its planning, its great arteries, its temples and its ports would be equalled only by its openness to the rest of the world. And the monumental achievements of its sovereigns, still shrouded in mystery, we'll never cease to fire our imagination for millennia to come.

The Hale-Bopp Comet is passing Earth and rumours of a mysterious object following the comet could mean the sign that the Heaven’s Gate community could be looking for. With plans for the Exit, the group members begin saying goodbye to the world. In the aftermath of the suicides, the world and the surviving former followers react.