In March 1997, investigators entered a California mansion to find 39 people lying peacefully in matching black clothes and brand-new Nike sneakers, each covered by a square purple shroud, each carrying exactly $5.75. To the world it was a horrifying mass suicide. To the people inside, it was a graduation.

This episode is a sobering look at Heaven's Gate and the human vulnerability behind it: how two people at rock bottom built a sealed reality that convinced intelligent, searching adults to surrender their families, identities, and finally their bodies for a promised ride on a spaceship trailing Comet Hale-Bopp.

• How Marshall Applewhite and Bonnie Nettles forged a shared cosmic mission and recruited a 'crew' rather than a congregation
• The doctrine of shedding 'mammalian traits,' including the voluntary castration of eight  ...