Don Quixote exits his chamber the next morning. The girl who had sung under his window the other night, Altisidora, swoons when she sees him. Her friend calls Quixote an ingrate and asks him to leave so Altisidora can recover. He asks for a lute to be left in his chamber so he can cure Altisidora.
That night, Quixote begins to serenade Altisidora. A sack full of cats with bells is emptied into his window. The sound is awful and causes everyone—including Quixote—to panic. The cats put out the lights trying to escape. Quixote manages to chase all but one out. The one jumps on his face, doing damage with its claws and teeth. The duke comes to his rescue. Quixote is angry that they interfered with his fight with the transfigured enchanter.
Altisidora tends to his wounds but says this is punishment for his disdain of her. She hopes Sancho doesn’t complete his penance, and Dulcinea remains enchanted. Quixote doesn’t reply. He thanks his hosts for coming to his aide. The duke and duchess regret the injury which they hadn’t foreseen as a consequence of their joke.