In 1997, dispatched to the suburb of Rancho Santa Fe, the San Diego Police entered a Mediterranean-style mansion and found 39 dead bodies. The deceased were uniformly dressed in black sweatpants, black button-down shirts, and new black-and-white Nikes. Each had $5.75 in his or her pocket. They had ingested phenobarbital dissolved in applesauce, followed by vodka, so that their spirits could “exit their human vessels” and be taken by spacecrafts—piloted by extraterrestrials—to a “higher evolutionary level.” These people were members of the Heaven’s Gate cult, founded two decades earlier in Houston, when Bonnie Nettles met Marshall Applewhite and the two came to believe that they were on an earthly mission to save souls. This four-part HBO docuseries, directed by Clay Tweel, looks beyond the story’s shocking and salacious elements to grasp at the human dynamics that drove the cult’s evolution and its horrifying conclusion. —C.J.F.