The novel relates two parallel storylines originating in Kitty’s refusal to marry Levin, favoring the handsome and dashing officer Vronsky.
From this act of vanity and levity, immediately undone by Vronsky falling in love with Anna Karenina, Levin’s trajectory begins: his love for the countryside, his rapprochement with Kitty culminating in marriage and the discovery of faith; while Anna’s sorrowful tale unfolds—her affair with Vronsky, the abandonment of her husband, their life together abroad, in the country, and in Moscow, down to her tragic suicide.
We are faced with an «official» plot, which would perhaps seek to express Tolstoy’s own thought and message: only an adherence to religious values and Russia’s traditional customs can save man and the nation, whereas vanity and hypocrisy, typical traits of the aristocracy, can lead to nothing other than personal destruction and the moral and social unraveling of a people.
The generous, profound Levin finds in the responsibilities of marriage, family, and estate management the answer to his social and existential inquiries.
It is not new production techniques, economic theories, or philosophers that provide him this answer; rather, life itself has granted him revelation through the consciousness of good and evil.

I have not acquired knowledge, but it was given to me...
because I, by my own strength alone, could not have attained it

.
The elegant and cultivated Anna, by contrast, having failed to honor ties with the traditional religious and social sentiments of Russia, is driven, in spite of herself, to despair:

how many things, (when I was a child) that seemed beautiful and unattainable to me in those days now seem wretched! And what I possessed then is now lost forever

.
Yet the contradiction between reason, which leads to death, and faith, which leads to life, persists up to the final moments of Anna’s life:

Yes, everything disturbs me, torments me.
Reason is given to us to free ourselves from what torments us.
Therefore, I must rid myself of it.
Why not put out the light, if one no longer wishes to see anything, if looking at things arouses nothing but aversion?....suddenly the darkness that now enveloped everything for her was pierced and life appeared to her for an instant with all its bright past joys...
Lord, forgive me everything! she uttered once more, feeling the impossibility of struggling.
The muzhik, muttering something, worked on the foundations

.
As the novel unfolds, the character of Anna Karenina assumes an autonomous life, one that transcends the author's own aims and endows her with qualities starkly distinct from those demanded by the official plot.
It is almost as though Tolstoy falls in love with his own creation, unable to confine her within the role originally conceived.
At first, it is clear that Anna is a hollow and vain figure, fully conforming to the false standards of the Russian aristocracy; gradually, however, the complexity of this character deepens as she pursues absolute love and an authentic life, far beyond the hypocrisies of society.
Anna is tormented by a profound sense of guilt over abandoning her husband and, above all, her son; yet she senses she is not guilty, for she wishes only to «live her life» in a sincere and genuine manner.
From this perspective, she cannot simply be defined as a romantic figure, since the love affair is significant but ultimately serves as the catalyst for a deeper spiritual yearning: the resolve to live out her freedom without hypocrisy and false conventions.
Anna Karenina is a tragic character who destroys herself and those around her, as though driven by a demon (the dream of the old muzhik) and by a destiny that surpasses her own will.
Over the course of the novel, a kind of «reversal» takes place—a profound shift in perspective that leads to the elevation of Anna’s character, outwardly fragile and culpable, over the duller and flatter Levin and Karenin.