In France, the starving English army is dogged by the French. If they can cross the River Somme they can reach the coast and escape, but all the bridges are down. Ralph, older, scarred and brutal, points out that the French army is being resupplied from the far side, so there must be a ford, or failing that, the estuary. Edward concludes that a forced march might reach it before the French are aware of the plan.
Kingsbridge is run-down, its market small and poorly stocked. Gwenda is now mother of two sons, Sam and David. When Gwenda goes to find Caris, now a professed nun, Wulfric is told to keep an eye on them. The instruction sounds like something repeated many times. As Caris rushes to help, she ignores the familiar sound of useless recriminations from Gwenda, none of which sound like an advertisement for loving couples.
Gwenda finds Caris praying by her parents' grave, and as they return to town they watch the arrival of Gregory, Godwyn's lawyer, whose presence never bodes well. Before they can find out what trouble he's brought this time, Caris has to rush to the assistance of young Sam, who sneaked away from his father's distracted attention, played with a stage-magician's fire-making equipment and set himself alight. He's lucky, it's not as bad as it seems, but Gwenda's weary recriminations indicate that all's not well between her and Wulfric.
For once Gregory has brought something pleasant: a rich bequest for Mother Cecilia, who announces that the convent now has money to enlarge Caris's one-room hospice. But Godwyn has also heard of the bequest and is taking unhealthy interest, even though he still hasn't built his palace, more concerned with hoarding wealth than using it. Since his spy Sister Elizabeth holds the keys of the convent treasury, Cecilia's bequest is far from safe.
Caris writes up Sam's case she keeps a hidden record of her work, along with books by Moorish physicians that would be condemned as Devilry - and Sister Mair suggests she should write her own medical book, in English. Later that night Mair gets a shock as she finds Thomas and Matthias in bed together. She tells only Caris, for Godwyn would execute both men, and is surprised when Caris dismisses her concerns. They're good men, and they're not betraying their wives. Mair wonders if Caris is more than just tolerant.
Further discussion is interrupted by Signor Caroli, back from Italy with a letter for Caris from Merthin in Florence. Though he also brings disturbing news of a disease called the Great Mortality, Caris finds the letter more upsetting: Merthin is successful, married, with a daughter, but still misses her and feels his life wasted. Sadly she burns the letter: that ship sailed long ago…
In France, Edward and his army are appalled to find that the French have outflanked them. They're trapped. There won't even be a battle: all the French have to do is wait for the English to starve.
Godwyn has inevitably got his hands on the bequest. When Mother Cecilia confronts him, he demands written proof that it was intended solely for convent use. There isn't any, and he keeps the gold himself. Mother Cecilia decides to appeal right to the top. Caris has gained private time with the King once before; he might give her a hearing again. Ignorant of what a war zone is really like, she sends Caris and Mair to France.
Thomas and Matthias pray in the cathedral, unwilling to be together, unable to be apart. But Thomas is still so secretive that Matthias is afraid to trust him. Thomas warns that knowing his secrets is dangerous, but Matthias no longer cares.
In Florence, Merthin's wife and daughter die of plague, and with nothing to hold him in Italy any more, he sets out for England.
Caris and Mair see first-hand what war has done to France: rape, slaughter and destruction. As the women huddle together for warmth one night, Mair turns the comforting embrace into something more; if Caris won't condemn Thomas and Matthias, her love must be safe too. Sickened by the brutality around them, willing to accept any affection, Caris doesn't stop her. Next morning, discovered by an English patrol, they're taken to the English camp for their own safety.
There, Edward is almost in despair. His army is helpless, the French King has sent terms of surrender and worst of all, that seems the only option left. Leaving his tent to be alone with his thoughts, he encounters Caris, who has hoped for just such a meeting. At first he has no time for Church squabbles but, impressed by her courage and persistence, realizes that is what's best about England. If he's still king after the coming battle, he promises to grant her petition.
Encouraged by her example, Edward decides that courage and persistence are what's required. He'll attack: it's the last thing the French will expect. Ralph is sent on an advance raid to kill the French sentries so that Edward's best weapon, his longbows, can cross safely. The raid is successful, the bowmen cross, and flay the astonished French army with a storm of arrows while Edward leads the rest of his army across the river. Victory is assured.
Edward keeps his promise, and soon Caris and Mair, bearing a petition in the King's own hand, are on their way back to England.