How much do we know about the Catholic Church's relentless struggle against the famous "Qatari heresy"? A terrible quote "Kill everyone, the Lord will recognize his own"?.. Do we know much about the "Qatari heresy" itself - one of the most interesting, original religious and philosophical systems of the Middle Ages? About a truly unique culture that has managed to have a hidden impact on the life of all of Western Europe?.. Before you is Otto Rahn's Crusade Against the Grail. A book that will open the way for the reader to understand know the "children of the true God" - the Cathars...