If Frederick doesn't get that money, he fears he'll never see Madame Arnoux again. Yep, he's still stuck on her.
He goes to Madame Dambreuse, claiming he needs 12,000 francs for Dussardier, who he says has committed a theft. She gives him the money but is definitely suspicious.
Frederick races over to the Arnoux house, but is told that they've already moved out. Yeah, he doesn't believe that for a second.
He tracks down Regimbart, who tells him that the lawsuit has already gone through. Regimbart ("The Citizen") tells him: "A regular hare-brained fellow! He burned the candle at both ends! The petticoat has ruined him! 'Tis not himself that I pity, but his poor wife!" (2.18.34). What a mess.
Returning home to an angry Rosanette, Frederick sees the hideous painting Pellerin has done of the baby. Rosanette mistakes his tears over the loss of Madame Arnoux as a shared expression of grief over the loss of the child.
Madame Dambreuse gets word from Regimbart's wife that the money she loaned her fiancé was for Madame Arnoux. She doesn't let on that she knows, but instead, has Deslauriers come over to "consult" on a legal matter.
Tapping into Deslauriers's own envy and desire for revenge, Madame Dambreuse discusses the debts that Monsieur Arnoux had once owed to Monsieur Dambreuse—debts that he had supposedly forgiven at Frederick's request.
Deslauriers—bitter that Madame Arnoux rejected his advances—tells Madame Arnoux to sell the debts at auction so that a debt collector can buy them and prosecute the Arnouxes.
Walking by the Arnoux house a few months later, Frederick sees a poster advertising the auction for all of their furniture.
Frederick assumes that Rosanette is behind the scheme, and he accuses her of being a liar. He says she's in cahoots with Sénécal. And that's when he leaves the house, vowing never to return.
One day, while Frederick is out enjoying a carriage ride with Madame Dambreuse, she proposes that they go to an auction. They just "happen" to go into the saleroom that has all of the Arnoux furniture. Frederick can't bear seeing all of Madame Arnoux's possessions displayed in such a rough manner.
He sees a "little chest with medallions and silver corners and clasps," and remembers how he had seen it in her apartment.
Just to torment him, Madame Dambreuse buys it.
Frederick shows Madame Dambreuse to her carriage and makes it clear that their relationship is over.
Now that those two relationships are shot, Frederick returns to Nogent, figuring he'll marry the young Louise. How bad can she be? She's uncultured but she'll do.
He arrives in town to the sound of church bells as Louise and Deslauriers emerge from a church—having just been married. Yep.
He returns to Paris to find that fighting in the street has ramped up again. He witnesses a public execution by a police officer: it's Sénécal killing Dussardier.