The story begins with a conversation between a merchant and a schoolmaster. The merchant is on a sabbatical of sorts; he's staying in a house by a certain river. The schoolmaster proceeds to tell the merchant an unfortunate story about the previous owner of the house, one Bhusan Saha, who was reputed to be the heir to a large fortune.
Bhusan Saha was a college-educated gentleman possessed of an unusually beautiful wife. Although his wife, Mani, reveled in her husband's generosity, she eventually became disenchanted with his passivity. The schoolmaster asserts that, under "the spell of modern civilization," man had lost the "God-given power of his barbaric nature" and "was therefore, neither successful in business nor in his own home." It transpired that Bhusan, hard-pressed for a way out of his financial troubles, was afraid to even broach the topic of his distress with his wife.
For her part, Mani eventually disappeared with her jewels. The story is that Mani, with her jewels intact on her person, had eventually committed suicide in the river.
In the story, Tagore uses situational irony to highlight the role of feminine and masculine energy in the area of attraction. He asserts that "the ordinary female is fond of sour green mangoes, hot chilies, and a stern husband. A man need not necessarily be ugly or poor to be cheated of his wife's love; but he is sure to lose it if he is too gentle." Here, Tagore describes the idea of polarization as a factor in attraction: opposites attract, just as the different poles of a magnet attract each other. In the story, instead of preserving his wife's love with his gentle submissiveness, Bhusan effectively causes his wife to respond with contempt and apathy.
Tagore also uses dramatic irony to characterize his short story as an allegory involving different manifestations of revered Hindu gods and goddesses. Dramatic irony is usually used by an author to create tension and mystery; in this short story, Tagore uses this literary device to perfection. At the end of the story, we learn that the merchant is the supposed Bhusan Saha from the schoolmaster's story, and his wife, Mani, is really Nitya Kali, a Hindu goddess who manifests herself in different forms. The intricate dance between feminine and masculine characteristics in each of Nitya Kali's manifestations is a representation of polarization in the realm of Hindu spirituality.
If you like, please refer to my answer about characterizations of Hindu gods and goddesses in the story.
Bhusan Saha and Nitya Kali.