January 1804. Hammersmith, London. A group of young men had begun patrolling the streets, in search of a ghost that had been terrorising the local population for the past five weeks; a locksmith had already died of fright after seeing the ghost and two more witnesses were reportedly at death's door . In one newspaper report, it was alleged that an elderly woman had been so terrified by the sight that it brought on "a dejection of mind" from which she did not recover. A brewers' servant named Thomas Groom later testified that "I was going through the church yard between eight and nine o'clock, with my jacket under my arm, and my hands in my pocket, when some person came from behind a tomb-stone, which there are four square in the yard, behind me, and caught me fast by the throat with both hands, and held me fast; my fellow-servant, who was going on before, hearing me scuffling, asked what was the matter; then, whatever it was, gave me a twist round, and I saw...