This article tells the story of an eighteenth-century medical pamphlet called An essay on the nature and cure of the King's Evil, deduced from observation and practice. This was written by John Morley (d. 1776/7), a wealthy Essex landowner who advertised free medical treatments. The pamphlet is one of many short tracts on scrofula produced after the ceremony of 'the royal touch' ceased with the death of Queen Anne. However, it merits special attention from historians of medicine and historians of the book because it was edited and reprinted many more times than other surviving scrofula tracts: 42 editions appeared between 1760 and 1824. This suggests significant popularity. The Essay is also of interest because the first 15 editions display changes and additions completed by Morley before his death in late 1776 or early 1777. Between these versions, Morley consistently refashioned his identity as practitioner and author. He also adjusted his portrayal of the intended readers of the pamphlet: in later editions, readers are recorded using the Essay in increasingly complex and autonomous ways to design their own medical treatments. The pamphlet is therefore testimony to the fluid relationship between practitioner and patient. It shows that seemingly simple, formulaic and easy-to-read forms like pamphlets and case studies could play a variety of complex and shifting roles in eighteenth-century medical encounters and the construction of healing knowledge.