Cide Hamete explains that the student Carrasco found out Quixote’s location from the Duke’s page, spoke to the Duke about his adventures with Quixote, rode to Barcelona to defeat Quixote, and finally stopped by the Duke’s castle on his way home to report on the results of his venture. When the Duke found out that Quixote and Sancho would be travelling home near the castle, he planned this one final hoax with Altisidora. Cide Hamete writes that the hoaxers were probably as mad as the two friends.
The Duke, the Duchess, and the student Carrasco go to great lengths to prove Quixote’s madness. They become passionately fixated on his deviance. Their absolute conviction that their worldview is true and Quixote’s is false is a kind of insanity in itself. Insanity, here, is blindness to the truth of multiple perspectives.
Meanwhile, Altisidora steals into the friends’ room, where Sancho is sleeping soundly and Quixote is lying awake. She tells Quixote that his neglect killed her for a little while. Sancho asks what she saw in the underworld, and she describes devils playing pelota (a game like squash or baseball), but using books instead of balls. One of the books was the second part of the history of Don Quixote, and they thought it such a bad book that they plunged it deeper into hell.
Although Altisidora has behaved maliciously toward Don Quixote, her account of hell is a friendly gesture toward the knight, because it affirms the reality of Don Quixote as he is in Cide Hamete’s novel, and not the foolish Quixote of the Avellaneda version.
Don Quixote tells Altisidora once again that he loves only Dulcinea, and she tells him angrily that she does not really love him, and that last night’s events were only a hoax. The Duke and Duchess also come to visit, and Quixote tells them that they should give Altisidora useful tasks to distract her from her infatuations. They agree that Quixote and Sancho will leave the following day.
Tosilos and Altisidora have both plainly said that certain events at the castle have been hoaxes, and Quixote can easily deduce that all the adventures there have been false ones. If that’s so, then Sancho cannot disenchant Dulcinea by lashing himself.