That glance means a great deal,’ she thought. ‘That glance shows the beginning of indifference.’ —Anna Karenina

“On the day before there had been almost a quarrel between Vronsky and
Anna over this proposed expedition [to the district elections]. It was
the very dullest autumn weather, which is so dreary in the country,
and so, preparing himself for a struggle, Vronsky, with a hard and
cold expression, informed Anna of his departure as he had never spoken
to her before. But, to his surprise, Anna accepted the information
with great composure, and merely asked when he would be back. He
looked intently at her, at a loss to explain this composure. She
smiled at his look. He knew that way she had of withdrawing into
herself, and knew that it only happened when she had determined upon
something without letting him know her plans. He was afraid of this;
but he was so anxious to avoid a scene that he kept up appearances,
and half sincerely believed in what he longed to believe in—her
“ ‘I hope you won’t be dull?’
“ ‘I hope not,’ said Anna. ‘I got a box of books yesterday from
Gautier’s. No, I shan’t be dull.’
“ ‘She’s trying to take that tone, and so much the better,’ he
thought, ‘or else it would be the same thing over and over again.’
“ ‘And he set off for the elections without appealing to her for a
candid explanation. It was the first time since the beginning of their
intimacy that he had parted from her without a full explanation. From
one point of view this troubled him, but on the other side he felt
that it was better so. ‘At first there will be, as this time,
something undefined kept back, and then she will get used to it. In
any case I can give up anything for her, but not my masculine
independence,’ he thought.”

Anna Karenina, Part Six, Chapter 25

“In solitude afterwards, thinking over that glance which had expressed
his right to freedom, she came, as she always did, to the same
point—the sense of her own humiliation.[…]’What has he done, though?…
He looked at me with a cold, severe expression. Of course that is
something indefinable, impalpable, but it has never been so before,
and that glance means a great deal,’ she thought. ‘That glance shows
the beginning of indifference.’

Anna Karenina, Part Six, Chapter 32
It’s an argument! It’s not an argument! No matter which side of this
meta-argument you take, it is hard to imagine a better rendering of
the way that misunderstandings can escalate into conflicts within the
context of a relationship. There’s Vronsky’s desire for masculine
independence (whatever that might be defined as), there’s Vronsky’s
perception of Anna’s smile as bullheaded concealment, there’s Anna’s
sense of being trapped in a unfulfilling relationship with Vronsky
(because of her inability to get a divorce from her husband), and
there’s Anna’s perception of Vronsky’s glance as fraught with
indifference. For a couple that began with such a direct, intimate
connection, they have come to a point where they are complete
strangers to each other.
The patient iteration of their relationship through the hundreds of
pages that it takes for Tolstoy to arrive at this point is what makes
the book into literature. Everyone has had a futile, unfulfilling
relationship; everyone has had a relationship that was a minefield of
misunderstanding. Back to the Chapter 32 quote: everyone, especially
in the relationship-saturated world of today, can understand how a
single glance can convey the “beginning of indifference.”