The book of Zoe Oldenburg, our compatriot, who left for France as a child and devoted her life to the hard work of a historian, is rightfully considered one of the fundamental works on the Albigensian Crusades and on the mysterious phenomenon of the Cathar heresy. The book is written clearly, not feminine rigidly and at the same time is distinguished by the emotional piercing that does not allow it to be read without deep excitement.