In 2017, Janet Reitman was reporting a story for Rolling Stone. It was about two months after the Unite the Right rally in Charlottesville, Virginia, and she was sitting in the living room of Walter and Chris Oneschuk, a couple whose 19-year-old son, Andrew, had just been killed. “He was a member of the Atomwoffen Division,” Reitman explains via Zoom. “They were a neo-Nazi group, and he had been murdered by another neo-Nazi kid that was in the group. It was a terrible story, and the parents were completely blindsided, as you can imagine. They kept saying to me, ‘I...