In the early evening of Thursday 16 December 1602, Satan departed from fourteen-year-old Mary Glover, the daughter of the staunchly Puritan Timothy Glover, merchant of Thames Street in London. Life returned to her body, and lifting her hands up high, she cried out ‘He is come, he is come’, and then, ‘The comforter is come. O Lord, you have delivered me.’ These were the words of her Grandfather, Robert Glover, we are informed, as he was going to be executed by burning.

Mary Glover was the granddaughter of Robert Glover, burned at Lichfield during the reign of Mary on 20 September 1555. For the Puritan John Swan, Mary, like her grandfather, is the victim of persecution both demonic and official. Swan's anger, like that of John Darrell and George More, is directed against Samuel Harsnett in his capacity as Chaplain to Richard Bancroft the Bishop of London, and discrediter of exorcists, both Catholic and Protestant. Harsnett had referred to Swan, along with three other Puritan ministers involved in the dispossession of Mary, as ‘devil-finders and devil-puffers, or devil-prayers’ in his A Declaration of Egregious Popish Impostures. It was both this defamation and Harsnett’s belief that ‘the opinions of witches [to] be brainless imaginations’ that motivated Swan to give us his very detailed account of a Puritan exorcism.

In prefacing his work with a letter to King James I, Swan was no doubt optimistic that he would receive a sympathetic hearing.