“The Cult Next Door”: “20/20” Diana Sawyer’s Special Program Explores the Gates of Paradise, Mass Suicide, Leader Marshall Appleyte

This is still the largest mass suicide ever on American soil: in 1997, 39 people on a ranch in Santa Fe, California, committed suicide because they believed that UFOs would carry them to a higher level of existence for all eternity.

Among the dead were nurses, veterans and even glorifiers who left their daily lives, careers, families, friends and even young children for the sake of the cult of the Heavenly Gate.

In the new two-hour special issue of “20/20” ABC News presenter Diane Sawyer and the team decipher the secrets of the cult and explore the secrets of its convincing leader Marshall Appleythe. Watch the trailer in the media player above.

In 1997, Sawyer conducted an exclusive interview with Rio Di Angelo, a member who left the group before the tragedy to serve as an envoy to the world. Twenty-three years later Sawyer was interviewed again.

Special programs feature exclusive never-before-seen tapes and intimate audio recordings of Applewhite, his followers, interviews with former participants emerging from the shadows, relatives of deceased followers and authorities working on the horrific affair. The two survivors are also sharing their experiences in cults for the first time.

“The Cult Next Door: The Mystery and Madness of Heaven’s Gate” airs “20/20” on Friday, March 11, at 9 | 8c on ABC and the next day on Hulu.