The fourteenth century would see Europe wracked by upheaval, war, rebellion, famine and plague. To many it seemed as though society itself was breaking apart, a true age of apocalypse. No institution was above the tumult. The Church, which had survived critics and outlived sects, found itself under virulent attack from heretics. It countered with the inquisition. Designed to identify, catch and suppress heresy, this notorious institution was born in south-western France and tasked with the destruction of the heretical Cathars of Languedoc. In 1307 Bernard Gui reached Toulouse to take up his appointment as inquisitor. For the next two decades he mounted a relentless campaign against the region's heretics and schismatics. Targeting Cathars, Beguins, Waldensians, relapsed Jews, sorcerers and 'those who invoke demons,' he worked hard to bring such 'twisting snakes out of the sink and abyss of error'. His experiences enabled him to pen this fascinating guide. It is a practical manual on the conduct of inquisitions intended for his colleagues and successors. It sets out, in a plain and readable manner, how to combat medieval heresy's assault on the Church. How to seek out, identify and capture heretics; how to understand their strengths and weaknesses; how to try them; how to counter their devious methods and prevent them from 'hiding behind deceitful words'; how judgement should be made and how punishment delivered. By so doing, Gui provides a wealth of information on the Cathars and on medieval life in general. Gui's manual is a fascinating insight into this tumultuous period, an insider's view of the infamous inquisition and a brilliant window into the medieval mind.