The men and women separate into different rooms after dinner, because that's what they did back in the day. Also, what's more, the guys want to talk about inequality of marriage rights, which they feel would be indecorous in front of the ladies.
For some reason the conversation keeps turning to unfaithful wives, making things super-awkward for Karenin.
Finally, Dolly gets him away into a private anteroom. She implores him to tell her about Anna. Dolly is convinced of Anna's innocence, and credits her with holding Dolly's own marriage together.
Karenin remains adamant that he must divorce Anna, while Dolly is convinced that would mean Anna's ruin. Karenin can't destroy his wife's life, Dolly argues.
Dolly brings up Oblonsky's infidelity, and tells Karenin that as she forgave Stiva, so he must forgive Anna.
Karenin finally gets angry, saying that he cannot and will not forgive.
He apologizes for upsetting Dolly and bids her a good night.