Tolstoy's great novel about an aristocratic woman who leaves her husband and son for a cavalry officer has an outstanding caste in this version.
Count Vronsky (Fredric March) drinks with officers in Moscow, and going with Stiva (Reginald Owen) he meets Stiva's sister Anna Karenina (Greta Garbo) at the train while welcoming his own mother (May Robson). Stiva's wife Dolly (Phoebe Foster) tells Anna that Stiva is involved with the governess, but Anna asks her to forgive him. Kitty (Maureen O'Sullivan) tells Anna about Vronsky although she also likes the farmer Levin. At a ball Levin (Gyles Isham) dances with Kitty, and Vronsky persuades Anna to dance with him. Anna returns to St. Petersburg on a train and finds Vronsky came to be with her. Alexei Karenin (Basil Rathbone) greets Anna at the station, and Anna goes home to her boy Sergei (Freddie Bartholomew). Karenin says Anna is spoiling Sergei.
Vronsky and Anna play croquet and escape the guests to talk. Anna tells him to marry Kitty. Vronsky says they are doomed to despair or bliss and kisses her. Anna feels guilty, but later she tells Vronsky she loves him. Anna kisses Sergei goodnight. Karenin warns Anna about causing gossip with Vronsky because of appearances. Anna tells Karenin he loves his career, not her. Vronsky's mother advises her son not to neglect his career, and Captain Yashvin (Reginald Denny) tells Vronsky the general may make him resign because of a lady. Vronsky goes to Anna and asks her to divorce so they can marry; but she won't leave Sergei. Anna watches Vronsky race; he falls and has to shoot his horse. Karenin takes Anna home and reprimands her. She admits she loves Vronsky. Karenin believes in marriage as a sacrament and won't give her a divorce or their son.
After a month with Karenin's coldness Anna goes to Vronsky, and he takes her to Venice, where they are both happy. Meanwhile Levin weds Kitty. Sergei calls for his mother, and his father says she is dead, though Sergei doesn't believe it. Vronsky's regiment is going to fight the Turks with the Serbians. Anna gets a letter from Karenin forbidding her to see Sergei. Anna has Vronsky go with her to the opera, and people whisper. Anna goes to Sergei on his birthday. He has been talking to her in the dark, and they are delighted to be together. Karenin tells Anna sternly never to come back.
Vronsky gets a letter from Yashvin, and he admits to Anna he promised to enlist in the war. She says he doesn't love her, and he goes. Anna goes to Stiva and Dolly's to meet Vronsky. Stiva agrees with Karenin that the sanctity of the home must be protected, but he is still stepping out. Dolly says there is always a penalty. Anna gets her letter back and goes to the station to catch Vronsky saying good-bye to Princess Sorokino (Mary Forbes) and his mother. Anna sits there until dark and then throws herself under the moving train. Vronsky can't forget that he didn't give her a kind word and feels guilty.
Anna's tragic conflict is that society's morals, represented by Karenin, will not allow her to love her son and Vronsky. She gave up everything for him; but he would not even give up war.