In the story, Mani is the pampered wife of a wealthy man, Bhusan. Although Mani lives a privileged life, she is vaguely dissatisfied with her marriage. For his part, Bhusan's life of ease seems to have robbed him of an intrinsic and vital part of his manhood.
Mani comes to take Bhusan for granted. She accepts caresses and priceless jewels from her husband with undisguised contempt and little gratitude. Mani does not understand Bhusan; she finds it difficult to relate to his atypically tame nature. There is little sexual attraction between the two.
According to the narrator, Mani's female nature yearns for the novelty of a masculine temperament untouched by modern civilization. He cites Bhusan's relinquishment of his "barbaric nature" as the main reason for Mani's apathy.
"The wife of a man who is, of his own accord, submissive is altogether out of employment. All those weapons which she has inherited from her grandmothers of untold centuries are useless in her hands: the force of her tears, the fire of her anger, and the snare of her glances lie idle."
Mani essentially rejects her husband and creates a separate, dynamic existence for herself within her marriage. She spurns her social obligations and neglects her religious duties:
"Bhusan's wife did not talk very much, nor did she mix much with her neighbors. To feed Brahmans in obedience to a sacred vow, or to give a few pices to a religious mendicant, was not her way."
(Note that the pice is an obsolete Indian denomination from the days of colonial India).
Instead, Mani puts all of her energy into building wealth; since she is "always working and saving," she is never "sick nor sorry." Mani's industry sustains her and preserves her enthusiasm for life. Essentially, she invests in her own happiness and ceases to rely on Bhusan for emotional fulfillment. When Bhusan begins to experience business difficulties, Mani acts to protect her own wealth. She retains Modhu's counsel.
The text tells us that, while Mani may not understand Bhusan, she is familiar with the sort of principles that actuate a man like Modhu. She knows that Modhu is compelled only by his own self-interest. With Modhu's help, Mani makes preparations to transfer all of her jewels to her father's house. Now, here's an interesting quote that explains why the lack of rapport between Mani and Bhusan eventually leads Mani to betray her husband.
"When he ought to have been angry, Bhusan was only distressed. Man is the rod of God's justice, to him has been entrusted the thunderbolt of the divine wrath, and if at wrong done to himself or another it does not at once break out into fury, then it is a shame. God has so arranged it that man, for the most trifling reason, will burst forth in anger like a forest fire, and woman will burst into tears like a rain-cloud for no reason at all. But the cycle seems to have changed, and this appears no longer to hold good."
Basically, Mani finds it difficult to "understand" Bhusan because she is operating from a different set of standards regarding gender roles:
"Bhusan, who ought to have been born five or six centuries hence, when the world will be moved by psychic forces, was unfortunate enough not only to be born in the nineteenth century, but also to marry a woman who belonged to that primitive age which persists through all time."
Mani's feminine nature yearns to unite with a primeval masculine nature. She can only understand what she innately believes about gender roles. Because Bhusan's mild nature doesn't fit into her personal narrative about masculinity, Mani rejects her husband. In the story, the narrator tells us that Mani is synonymous with Nitya Kali, a goddess who represents endless time. Basically, the author hints that Mani's lack of understanding stems from her refusal to accept anything other than a primal interpretation of gender roles.