Over the Independence Day weekend in 1960 a young police officer is murdered, shocking his close-knit community in Stamford, Connecticut. The killer remains at large, his identity still unknown. But on a beach not far away, a young Army doctor, on leave from his post at a research lab in a maximum-security prison, faces a chilling realisation. He knows who the shooter is. In fact, the man-a prisoner out on parole-had called him only days before. By helping his former charge and trainee, the doctor, a believer in second chances, may have inadvertently helped set the murder into motion. And with that one phone call, may have sealed a policeman's fate.

Alvin Tarlov, David Troy and Joseph DeSalvo were all born of the Great Depression, all with grandparents who'd left different homelands for the same American Dream. How did one become a doctor, one a police officer and one a convict? In Genealogy of a Murder, journalist Lisa Belkin traces the paths of each of these three men-one of them her stepfather. Her canvas is large, spanning the first half of the 20th century: immigration, the struggles of the working class, prison reform, medical experiments, politics and war, the nature/nurture debate, epigenetics, the infamous Leopold and Loeb case and the history of motorcycle racing. It is also intimate: a look into the workings of the mind and heart.

Following these threads to their tragic outcome, Belkin examines the coincidences and choices that led to one fateful night. The result is a brilliantly researched, narratively ingenious story, which illuminates how we shape history even as we are shaped by it.