America in the spring of 1963 is fixed in the collective memory as a time of innocence, a time of confidence. Kennedy was on his throne in Camelot, and violence and murder had still to mar the progress being made by the civil rights movement. Yet every golden age has its Mordred. That spring, the suburbs of Boston were living in fear, terrorised by a man who had strangled eight women since the previous summer. One afternoon in March, he came to the cosy dormitory town of Belmont and killed his ninth victim, a housewife named Bessie Goldberg, who lived a few minutes’ walk from the home of the infant Sebastian Junger.

This time the police got lucky. A black man had been seen near the Goldberg house, his colour enough to warrant attention in a community as solidly white as its picket fences. Roy Smith, a drifter with a long criminal record who had worked that afternoon for Mrs Goldberg as a cleaner, was soon arrested.

A clerk in a liquor store said that he had seen Smith produce a ten-dollar bill and five ones from his pocket (the same denominations as had gone missing from Bessie’s bedside table), and despite his protestations of innocence Smith was convicted and sentenced to life imprisonment. That the murder