In a prologue, we learn that the narrator is called Silence because no one wants to listen to her. Her companions in the castle are occupied with vanities or the concerns of daily life, such as food, clothes, farming and trade. They are bored of books or waiting for a prince or a knight to enter their chambers and sweep them off their feet. So the narrator is not going to tell her story for them, or for the men away at war, but for those who are yet to be born. Arturo is king of Galicia, and Galicia prospers under his rule – there is maize, fish and meat for everybody. But enemies are always threatening their borders, and the king, who has two sons – Afonso and Pedro – is concerned about the question of succession. He does not agree with the idea that the firstborn should inherit the throne, in case the firstborn is not suitable or simply prefers to lead a quiet, untroubled life, and both his sons have their merits. While pondering this question, he falls into a slumber, and in his dream his more famous predecessor, King Arthur, appears to him and provides him with a solution. He will make two keys, one of gold, the other – a replica – of iron. Both will open the doors of the kingdom, but while the gold key will bring prosperity and good fortune, the iron key will spell disaster and destruction. The king consults the sage Merlin, who lives on top of the world, where he can see the whole of time, without a before or an afterwards, who advises that the keys must be handed to their owners without anyone knowing which is which, and it will be fortune who decides which of the sons ascends to the throne.

When his sons are grown men and about to set off for war, Arturo summons them and hands them each a key. The elder brother, Afonso, is noble, so noble he can be cruel and selfish. If he inherits the throne, he will be able to maintain order, but if his key is the iron key, then his people will fear him. His retinue is made up of the finest courtiers. Pedro is kind-hearted and artistic. He runs the risk of being taken advantage of, and his retinue is made up of disorganized plebeians who are, however, devoted to him. When news reaches Afonso of Arturo’s death, he sends his trusted knight Roi Soares de Paiva to inform Pedro of their father’s death and then to arrest him – not to send him into exile, as their father had wished, but to kill him after retrieving the other key. Roi Soares arrests Pedro, who is attending assiduously to his men and at the same time fighting the enemy. Pedro refuses to hand over the key, so Roi Soares escorts him to the palace. On the way, they stop at a castle that has been taken by the forces of Queen Eleonora under her commander-in-chief, Alvar de Morasilla. Alvar plans to marry the lady of the castle, María das Augas Doces, the very next day. He relieves Roi Soares of his prisoner and tells him to go to his king and arrange a treaty between them, otherwise Alvar will kill him and replace him with his younger brother. Roi Soares, accompanied by some of Alvar’s men, sets out to the palace, without their prisoner, and they spend the night in Lamela, a town that used to be prosperous, but is now all shut up out of fear of brigands.

Alvar comes to María’s rooms to ask/tell her to prepare for their wedding the next day. He doesn’t have much experience of women and thinks of love as an exercise that is similar to warfare – you go in with your weapons raised until victory or weariness forces you to lower them. María, who is a widow, her young husband having fallen in battle almost without approaching her bed, says if she must marry the next day, it will be against her will. She seems to have a plan. At the inn in Lamela, Roi Soares is unaware of the displeasure his arrival has caused the innkeeper, Laredo (“Master Touciño”). He sits away from the soldiers and drinks in the company of a hired assassin, Armada, asking him if he would be prepared to join him against the king, Afonso. In the meantime, Pedro suffers cold in the dungeons of the castle, where he is imprisoned. He thinks of the dungeon that is every man’s life, but doesn’t wish to die in order to escape these earthly chains, since he has been intoxicated by María’s beauty. María herself would much prefer to have Pedro as an invading army than the fat and gluttonous Alvar, whom she is due to marry in the morning, and she determines to visit the dungeons that night. A girl keeps the soldiers company in the inn in Lamela and provides them with wine, but when one of the company seeks to grab her from behind, Armada springs to his feet and threatens him with his sword. The soldiers go to rest; the girl enters the room she has prepared for Armada upstairs.

While a lady-in-waiting, Helena, entertains the guard who has been placed at the door of the dungeon, María goes to free Pedro, leading him along secret passageways and out into the open, where two horses, clothing, gold and food, enable them to escape. Meanwhile, Armada and the other soldiers lead their prisoner, Roi Soares, in the direction of the palace, where Afonso awaits. In the castle, preparations are underway for the wedding that is due to take place. Alvar has summoned the abbot of a local monastery and waits in the castle church for his bride to appear, but the woman who approaches the altar is not María – it is her trusted confidant, Isabel. Alvar is furious, the other guests are relieved. In his palace, Afonso is convinced he is the best person to rule the kingdom. He prefers the company of his loyal knights, but keeps his father’s advisers close, in case they should decide to favour his brother, Pedro, and doesn’t pay much attention to the women. Now is not the time for marriage, there are more important matters to attend to. He is surprised to learn of Pedro’s imprisonment and the approach of Roi Soares as hostage and messenger.