In the late 1990s, the world was shocked by the mass suicide of 39 members of a New Age religious sect. They believed that their souls would go to an alien spacecraft behind the Hale-Bopp comet. Co-founded by Marshall Applewhite, who once called the group "the cult of cults," and Bonnie Nettles, Heaven's Gate began in 1975 with the mysterious disappearance of 20 people from a small Oregon town and ended in 1997 with the largest suicide on record. American soil. Using never-before-seen footage and personal stories from former members and their loved ones, this four-part docuseries is a thorough investigation into the infamous UFO cult that stunned the world with their alien beliefs.