A historical investigation that examines how, at the end of the 16th century, the devilish acts of Marthe Brossier, who claimed to be possessed, led her contemporaries to refine their thinking on the relationship between religion and science, between God and the state. Four historians dissect this plot hatched by ultra-Catholics against King Henry IV at this juncture in history marked by the end of the Wars of Religion and the birth of the state in an unstable society where the difficult genesis of a new world was looming. Our world.