I grew up on Long Island, New York in the 1980s/90s, a time when—despite all the picture-perfect middle-class suburban trappings—there was no shortage of salacious scandals and horrifying crimes being committed. It seemed there was a Satanic Panic story in the news every few weeks.

I’d heard about the infamous Northport cult killing a few years before reading the popular book based on the incident, SAY YOU LOVE SATAN. On June 19, 1984, three teens were involved in the murder of their friend w...