Some extraneous elements incorporated into the screenplay were not found in either source, including details about the plague, which were supplied by Russell's brother-in-law, a scholar of French history. Upon studying Grandier, Russell felt that he "represented the paradox of the Catholic church...  Grandier is a priest but he is also a man, and that puts him into some absurd situations." In Russell's original screenplay, the role of Sister Jeanne of the Angels, the disabled Mother Superior, was significantly larger, and continued after Grandier's execution. However, in order to shorten the lengthy screenplay, Russell was forced to cut down the role.