At the ball, the King and Queen are slated to perform the King’s favorite dance. It’s called La Merlaison and everyone in the city is excited
Preparations are made throughout the day for the fête, and at midnight the King finally arrives, looking "dull and weary."
All the notables at the ball have their own dressing rooms; before entering into his, the King asks to be informed when the Cardinal arrives.
Half an hour later, the Queen arrives and is subject to the same adulation as the King. She too looks "dull and weary."
The Cardinal shows up and looks straight at the Queen. He’s overjoyed when he sees that she’s not wearing any studs. He goes straight to inform the King, who immediately runs to the Queen and asks why she’s not wearing the studs.
The Queen gives an excuse and the King tells her that it’s not good enough and that she needs to put on the studs. She replies that she will have someone fetch them from the palace.
Everyone at the fête is confused: they saw the King and Queen talking, but they didn’t hear what they said.
The King comes out looking dashing in a hunting costume.
The Cardinal approaches and gives the King a small casket containing two diamond studs. He explains that if—laying emphasis on the if—the Queen has the studs, she will be missing two of them. In that eventuality, the Cardinal tells the King to ask the Queen who could have stolen the missing two.
The King is about to reply to the Cardinal when the crowd erupts in admiration for the Queen. The Queen was dressed as a huntress and emerged wearing "a beaver hat with blue feathers, a surtout of gray-pearl velvet, fastened with diamond clasps, and a petticoat of blue satin, embroidered with silver. On her left shoulder sparkled the diamond studs, on a bow of the same color as the plumes and the petticoat."
The King is happy and the Cardinal is angry at the sight of the diamond studs! The Queen is still too far away to count the number of studs on her shoulder.
And the ballet begins! As they dance, the King keeps trying to count the diamonds, but to no avail.
Finally, the King goes over to the Queen and is all, I think you lost these.
The Queen looks surprised and says she now has fourteen. Twelve diamonds in total sparkle on her shoulder.
The King calls the Cardinal over and demands an explanation.
The Cardinal gives a made-up explanation. Queen: 1, Cardinal: 0.
D’Artagnan stands in the crowd watching the scene play out; he alone understands what is really going on. He’s about to leave when a mysterious woman clothed in black gestures for him to follow her.
She leads him down all sorts of passageways and finally leaves him alone in a room. He hears ladies chatting, the Queen included. He waits.
Finally "a hand and an arm, surpassingly beautiful in their form and whiteness, glided through the tapestry." D’Artagnan falls to his knees and kisses her hand. The hand withdraws and leaves behind it a diamond ring.
Madame Bonacieux returns and tells D’Artagnan to go home. He protests. She tells him that a note awaits him at his apartment, and he obeys her unthinkingly. (According to the narrator, this means that he’s in love.)