Lucía receives a letter from her mother on her deathbed and decides to go to the Beguinage where she is. There she discovers that her death was not natural and she begins to investigate it.

In the Beguinage, they have to choose Lucrecia's successor as Great Lady, while Lucía discovers that her mother was poisoned and is determined to find out who killed her.

The news of Lucrecia's murder reaches the Avellanedas and the Beguines point out Catalina as a spy. Lucía defends her, certain of her loyalty and steels herself to discover the truth. With the help of Telmo, Lucía meets a hired thug who was unable to kill Lucrecia and who commits suicide shortly after, which arouses suspicion towards the Avellanedas. Munio's pressure causes the beguinage to lose benefactors. Guilty, Lucía helps with the sale of her wedding dress. A gesture that puts her at odds with Rodrigo and jeopardizes her stay in the beguinage.