On the night of the ball, the King arrives late and seems annoyed when he sees that the Queen is not wearing the diamonds he asked her to wear. Looking miserable, she murmurs that she did not want to wear them because she was afraid they might get lost. This obviously annoys him. 

The King and Queen go to their private dressing rooms to prepare for the first dance. When the King emerges, Cardinal Richelieu approaches him and says that the Queen does not have her diamonds—or if she does, she is missing two. To prove it, the Cardinal hands the King a small box containing two diamonds. He urges the King to ask the Queen how she lost them.

But when the Queen emerges from her dressing room, she is wearing the diamonds. She looks radiant, but the King is suspicious. Could she be missing two of them? They are dancing with different partners during the first dance, so the King spends the entire hour in an agony of suspense.

As soon as the dance is over, the King stalks over to the Queen and says stiffly that he is returning two of her diamonds. She pretends surprise and says that now she has fourteen instead of just twelve. The King counts her diamonds and, sure enough, he sees that the Queen has the entire set he gave her.

Cardinal Richelieu has been beaten again, and he knows it. To back out of the situation as gracefully as possible, he claims that he wanted to give the Queen two more diamonds himself, so he contrived a little joke in order to do it. D’Artagnan, watching from his guard post on the front steps, sees what is happening and grins.

Just as d’Artagnan is about to leave the Louvre that evening, Madame Bonacieux appears and beckons him inside. He follows her through a winding series of hallways. Several times, he tries to get her to stop and talk, but she tells him to be quiet. Eventually she leaves him in a small chamber outside a dressing room. From there, he can hear a conversation between women. As he sits quietly, listening, he realizes that he is listening to the Queen and her ladies in waiting.

Suddenly a hand emerges from the dressing room through a part in a curtain. D’Artagnan realizes that it belongs to the Queen. His reward for all his troubles is an opportunity to kiss her hand. He does so gratefully, and in the process, she slips him a beautiful diamond ring.

D’Artagnan puts the Queen’s ring on his finger and waits. Madame Bonacieux returns and tells him to go home. He reminds her that he undertook his journey to England partly for her sake. She replies that he has indeed earned a reward from her, and that she has already sent a note to his house. Hearing this, he leaves happy.