The novel opens with a scene introducing Prince Stepan Arkadyevich Oblonsky ("Stiva"), a Moscow aristocrat and civil servant who has been unfaithful to his wife Darya Alexandrovna ("Dolly"). Dolly has discovered his affair with the family's governess, and the household and family are in turmoil. Stiva's affair and his reaction to his wife's distress show an amorous personality that he cannot seem to suppress. In the midst of the turmoil, Stiva informs the household that his married sister, Anna Arkadyevna Karenina, is coming to visit from Saint Petersburg. Meanwhile, Stiva's childhood friend, Konstantin Dmitrievich Levin ("Kostya"), arrives in Moscow with the aim of proposing to Dolly's youngest sister, Princess Katerina Alexandrovna Shcherbatskaya ("Kitty"). Levin is a passionate, restless, but shy aristocratic landowner who, unlike his Moscow friends, chooses to live in the country on his large estate. He discovers that Kitty is also being pursued by Count Alexei Kirillovich Vronsky, an army officer. Whilst at the railway station to meet Anna, Stiva bumps into Vronsky who is there to meet his mother, the Countess Vronskaya. Anna and Vronskaya have traveled and talked together in the same carriage. As the family members are reunited, and Vronsky sees Anna for the first time, a railway worker accidentally falls in front of a train and is killed. Anna interprets this as an "evil omen." Vronsky, however, is infatuated with her. Anna is uneasy about leaving her young son, Sergei ("Seryozha"), alone for the first time. At the Oblonsky home, Anna talks openly and emotionally to Dolly about Stiva's affair and convinces her that Stiva still loves her despite the infidelity. Dolly is moved by Anna's speeches and decides to forgive Stiva...
(Excerpt from Wikipedia)