One of the families that dominated the thirteenth century were the de Montforts. They arose in France, in a hamlet close to Paris, and grew to prominence under the crusading fervour of that time, taking them from leadership in the Albigensian wars to lordships around the Mediterranean. They marry into the English aristocracy, join the crusade to the Holy Land, then another crusade in the south of France against the Cathars.

The controversial stewardship of Simon de Montfort (V) in that conflict is explored in depth. It is his son Simon de Montfort (VI) who is perhaps best known. His rebellion against Henry III of England ultimately establishes the first parliamentary state in Europe.

The decline of the family begins with Simon's defeat and death at Evesham in 1265. Initially they revive their fortunes under the new king of Sicily, but they scandalise Europe with a vengeful political murder. By this time it is the twilight of the crusades era and the remaining de Montforts either perish or are expelled. Eleanor de Montfort, the last Princess of Wales, dies in childbirth and her daughter is raised as a nun.