The castle of Coucy is a huge building on a hilltop in Picardy. There are five towers and a donjon—a central citadel—capable of housing a thousand people, even for a prolonged period such as during a siege. The castle is built in 1223 while there are many great buildings being constructed. Most take many years for completion but the castle at Coucy is finished in seven years. It is said there is a famous motto attached to the castle that reads: "Not king nor prince, Duke nor count am I; I am the lord of Coucy."

Into this life Enguerrand VII is born as ruler of Coucy. He is, by most accounts, an honorable man who is anxious to serve his country. It is that trait which puts him among several noblemen held as hostages in England after King Jean—then King of France—is captured by English forces. Jean is released with the agreement that France will pay a ransom. Enguerrand and other noblemen are held hostage until the ransom is paid. Collecting taxes sufficient to pay the ransom takes years and during that time Enguerrand meets Isabella, the adult daughter of the King of England. Isabella is an independent woman who has narrowly avoided several marriages. It seems likely that she and Enguerrand come to the conclusion to marry of their own free will, though the King of England is in favor of the match. They are married in England and the King grants Enguerrand his freedom upon that event. In addition, Enguerrand is given English lands that had been the property of his mother but withheld from the Coucys for many years.

Enguerrand and Isabella soon travel to France and there their first daughter, Philippa is born. The couple go back to England while the child is an infant and Isabella later gives birth to another daughter, Marie. Enguerrand is torn by his loyalty to France—the country of his birth—and to England, the country of his wife's birth and family. Isabella soon returns to England for good where she dies. Enguerrand has limited contact with Philippa but arranges for the marriage of Marie to Robert de Bar and that couple have a child before Robert falls victim to the Black Death. After Isabella's death, Enguerrand remarries and fathers another daughter. Enguerrand also fathers an illegitimate son, Perceval, who is formally recognized by Enguerrand and is known as the "Bastard of Coucy."

Enguerrand remains active in the business of France until well into his fifties when he serves in a campaign to oust the Turks from Hungary. He is captured and held prisoner. Though France is working to raise the money to ransom those captured, Enguerrand does not live to see France again. His wife and daughter Marie fight over the Coucy estate which is later sold off and eventually becomes property of the crown. King Henry IV is a direct descendant of Enguerrand's daughter, Marie.