After a civil war, Queen Isabella defeats and imprisons her husband King Edward II, crowning their young son Edward III but in reality keeping power for herself and her lover Lord Mortimer. Lawlessness is the real ruler of England.
A knight pursued by two enemy soldiers takes a crossbow bolt in his arm near the town of Kingsbridge and flees into the forest, where Merthin and Ralph, teenage sons of the Earl of Shiring, are practicing sword-fighting. Ralph reveals himself a cunning and ruthless fighter. They're interrupted by the wounded knight, who kills his pursuers and then asks the boys to take him to Kingsbridge Priory.
In Kingsbridge marketplace rumors are already current that the imprisoned King has been murdered, but Caris Wooler, daughter of the town's richest merchant, pays them no heed. She's more concerned with getting medicine for her sick mother from the town wise-woman, Mattie. Prior Anthony and Mother Cecilia of the neighboring convent are discussing also discussing medicine as it affects Anthony's nephew Brother Godwyn, who hopes to study it at Oxford if someone - Cecilia and the nuns - pays his way. The need for such study is shown by Brother Joseph's disgusting treatment of the wounded knight's arm, using dung as a poultice on the open wound. Wise-woman Mattie, summoned by Mother Cecilia, tries to help but as a mere woman her advice is overruled, and when Godwyn sides with Joseph's primitive methods, Cecilia makes it clear she won't pay for his studies.
Afterwards Anthony and Cecilia discuss the knight, Thomas Langley, who wants to become a monk. He's sponsored by the Queen herself and sends her a letter to confirm it, but Mother Cecilia wonders how he gained such favor, especially since rumors are about that the imprisoned King Edward has been murdered. Prior Anthony doesn't even want to talk about it. Neither of them are aware that later, after dark, Thomas buries something in the Priory garden.
There's little grief in Westminster either at Edward's funeral or his funeral feast. Kingsbridge supported the King, something that will come back to haunt it. Sir Roland, an ambitious knight, is already putting himself forward as the new earl, while young Edward III, ignored as subordinate to his mother, is well aware that Mortimer is her lover and plans to be much more.
Godwyn's mother Petranilla, Prior Anthony's sister, also has plans. She'll sponsor his studies with the sale of her house, and move in with her other brother, Edmund - making room by murdering his wife Rose, Caris's mother. The poison is augmented by Brother Joseph's hog-butcher doctoring, and Rose dies in agony. But matters get even worse when Rose's funeral is interrupted by Sir Roland and his soldiers, here to purge Kingsbridge of the late King's supporters - including Edmund and Sir Gerald.
All are condemned and the ex-Earl's sons are forced into service, Ralph as Roland's squire, Merthin as apprentice to brutish builder Elfric, but Petranilla, once betrothed to Roland, uses this old acquaintance - and bribery - to buy Edmund's life. However Roland cruelly orders his legs broken as a reminder of his crime. The rest hang, while jobless mercenary Joby, his son Holger and daughter Gwenda pickpocket their way through the execution crowd. Later, when Joby tries to rape Gwenda, Holger threatens to kill him, and decides a life in the army will be better than this. Gwenda however is weary of wandering and prefers to stay in Kingsbridge. Armed with a knife and ready to use it, the next time Joby tries to lay hands on her, she cuts him and drives him away.
Thomas Langley's letter reaches Isabella. She's unsettled by correspondence from someone Mortimer claimed was dead. The letter is thrown on a fire, but enough survives for young Edward III to learn that the man who vanished on the night of his father's death is in Kingsbridge. That, and his mother and Mortimer's reaction, is enough evidence to confirm his suspicion of what really happened.
Mattie splints Edmund's legs, giving him a chance to walk again, but Thomas loses his gangrenous arm and almost his life because Brother Joseph can't even amputate properly. Only Mattie and Caris, now her apprentice, are able to save him, but Brother Joseph, outraged, calls Mattie a witch, a word she will hear again in the worst possible way.
Ralpha and Merthin both suffer abuse as squire and apprentice, Elfric in particular being quick with a kick or blow. And the first signs of affection between Merthin and Caris are crushed when, to restore Edmund's fortunes, Petranilla arranges a profitable arranged marriage. Caris's husband will be Elfric, and her father's pathetic gratitude means she daren't refuse.
Convinced enough by the burned letter to take drastic action, Edward III drags Mortimer from the Queen's bed and sends him to the gallows. He grimly reminds his mother of who wears the crown in England, but as Caris breaks Merthin's heart by going through with her wedding in Kingsbridge Cathedral, Isabella swears revenge on the town that shelters Thomas Langley and caused her lover's death.