When the story opens, young Miranda is living in a convent of Begines, an order of "galloping nuns" who take only temporary vows. Her parents are dead and her younger sister, Alcidiana, lives with an uncle. The seeming unattainability of the Begines makes them more desirable to men, and Miranda is beautiful, accomplished, and wealthy. Not surprisingly, she has many admirers; she receives their gifts and attention with pleasure, while loving none of them. Then one day she meets Henrick, a handsome young prince who has taken monastic vows and changed his name to Francisco. (Miranda's maid tells her about Henrick's tragic past in a story within a story.) Miranda becomes infatuated with Henrick. When he rejects her advances, she accuses him of rape and has him thrown in prison.
Soon afterwards, Miranda meets Prince Tarquin and the two marry, but Miranda's extravagant lifestyle soon sees her wealth greatly reduced. She invites her sister to move in with her and Tarquin so that she can pilfer from her sister's funds. To keep a hold over her sister, she rebuffs all of her sister's suitors until Alcidiana moves out. Miranda then sends a servant to poison Alcidiana, which he does, but Alcidiana does not die and the servant reveals Miranda's plan to the authorities. The servant is hanged, and Miranda, due to her position, is only shamed, though a great sum of money is owed to Alcidiana and Tarquin is ordered to pay it by the court. Miranda talks Tarquin into killing her sister, and so he attempts to shoot her but fails. He is caught, confesses, and is sent to be beheaded, but the executioner misses the mark and hits Tarquin's shoulder instead, causing severe injury. Tarquin is then released, and he and Miranda leave the country. In the closing lines, it is noted that Miranda eventually repents her sinful past and that Tarquin has since died, though no explanation is offered for his death.