Some 15 years ago, as I was reading Loren Coleman’s classic book Mysterious America, one story in particular caught my imagination, and over the following months and years I became mildly obsessed with it.

In September 1944, a series of peculiar events rocked the town of Mattoon, Illinois. For almost two weeks, the town’s police department received dozens of reports from terrified residents that a mysterious prowler, dressed entirely in black, was haunting the streets and squirting anæsthetising gas into the faces of his victims. The reports got weirder. One described the mysterious felon as wearing a strange metal helmet or mask; another spoke of a Bigfoot-type creature.

Although the attacks petered out in mid-September, the events of that fortnight have since achieved near-mythical status.