Despite what she told Vronsky, Anna has been longing to come clean to her husband about her affair.
So after confessing everything to Karenin after the races, Anna feels better. She feels that despite what may come, her position will be clear, and there will be no more need for lying or deceit.
The next morning, Anna wakes up and thinks about what she said to her husband. She is horrified and wishes that she hadn't said everything that she did.
Then she thinks about Vronsky, whom she saw last night but didn't tell. She realizes that she kept quiet because she was ashamed.
Anna realizes that her husband has the power to drive her out of her house, and she feels like a burden to Vronsky.
This line of thought leaves her with nowhere to go. Anna can't make up her mind about anything, and has no desire to interact with anyone.
Anna's maid Annushka comes in, saying that she thought she heard a bell. Annushka gives Anna a note from Betsy, inviting Anna for a game of croquet.
Anna dismisses her maid, and continues feeling completely lost. Although she repeats "my God!" over and over again, she knows that religion cannot help her, in the same way that Karenin cannot help her.
She clutches her hair with both hands.
Annushka comes in to tell Anna that her son is waiting for her.
The idea of her son jerks Anna out of her hopelessness and gives her a direct goal. She can't leave her son. She decides that she must take her son and go away.
She goes down to breakfast and spends time with her son for a while.
Later, she decides that they will go to Moscow, taking only Annushka, Seryozha, and bare necessities.
She goes back to her room to write notes to Karenin and Vronsky.
She writes to Karenin that she can no longer remain in the house and that she is leaving with their son.
She begins a letter to Vronsky, but can't finish it.
She tells her staff that she is leaving that evening for Moscow, and begins packing.