It was the summer of 1972 when Spring Hill, a Washington, D.C., suburb, got its first taste of an increasingly violent, insecure modern world. The quiet residential area, whose inhabitants traditionally left their doors unlocked and spent the summers attending one another’s cookout, was rocked by the news that 12-year-old Boyd Ellison had been raped and murdered, his body dumped behind the local mall. While shaken residents organized a neighborhood watch program and clued detectives in on anyone’s suspicious behavior, the inhabitants of ....