Anna Karenina Part 1, Chapters 28-33
Anna decides she needs to leave Moscow and return to St. Petersburg, where her life is. Anna tells Dolly that she knows she ruined the gala for Kitty by flirting with Vronsky. Yet Anna contends the whole thing really wasn't her fault. Dolly makes an important note at this point: Anna denies blame in the same way Stiva does. This makes Anna, quite frankly, a liar.
"'Yes,' Anna went on. 'Do you know why Kitty didn't come to dinner? She's jealous of me.... I've been the cause of that ball being a torture to her instead of a pleasure. But truly, truly it's not my fault, or only my fault a little bit,' she said, daintily drawling the words 'a little bit.'" Part 1, Chapter 28, pg. 104
Anna leaves, laden with shame and guilt. She knows she's running from Vronsky, but she also knows she doesn't want to return to her husband. This haunts her. At one of the train stops, she needs to step outside for air to clear her head of guilt. Instead of a clean conscience, her head is filled with the sharp sounds of a worker hammering on the metal tracks.
When Anna arrives at the St. Petersburg station she immediately sees her husband. She feels freshly guilty for not appreciating his devotion. Nonetheless, she immediately begins to notice all of her husband's physical imperfections. She compares him to Vronsky. Up until now, nothing sexual has happened between Anna and Vronsky--if she has cheated on her husband, then it has only been in her heart. Yet the moments of tension and surprise are building between her and Vronsky. Something major is bound to happen, and it is becoming rather clear to her now that she needs to leave her husband in order to find some sense of happiness.
Anna goes home with her husband and sees her loving son Seriozha. Even he is not as wonderful as Anna remembered. That realization is hard for Anna, because it solidifies that the only exciting things in her life at this point are the little encounters she has with the mysterious count. Karenin doesn't make much of an effort to spend time with his newly returned wife. We see that, at home, Anna isn't remotely as radiant as she was in Moscow--there she was passionate and alive. At home, she is bored and disgruntled.