When Vronsky falls, Anna is extremely shaken and feels like a trapped bird. She begins to weep. An officer says that Vronsky is unhurt, and Anna continues to sob, but now out of relief. She wonders if Vronsky will still come to see her tonight.
Anna’s reactions at the race are entirely tied to Vronsky’s well being as it relates to her. When he falls, she feels trapped, and when he is well, her first thought is to wonder if she will still see him that night.
During the carriage ride home, Karenin rebukes Anna for behaving improperly. When Anna does not respond for a moment, Karenin thinks she will laugh away his suspicions. However, she confirms Karenin’s accusations, telling him that she is Vronsky’s mistress, that she is in love with Vronsky, and that she hates Karenin.
When Anna does not respond to Karenin immediately, it is not because his accusations are false but because she can only think about Vronsky. Anna cannot lie outright: she tells her husband the truth about the affair and her emotions.
Karenin stiffly asks Anna to keep up appearances. Anna receives a note from Vronsky saying that he would still come that night, and her husband seems like a dim recollection.
Karenin wants to maintain his social reputation at all costs, even though his actual marriage is crumbling. Anna only has thoughts of Vronsky.