I think that the relationship between Ratan and the postmaster symbolizes his lack of loyalty. To a great extent, Tagore constructs the postmaster's character as one who is looking for something else. The postmaster is discontent with his life in Ulapur, and is constantly on the lookout for something else. Tagore suggests that the relationship he shares with Ratan is more of a "distraction," something that can pass the time. In this, there is much in way of significance in terms of the characterization of the postmaster. His relationship with Ratan, the intensity of it, and the complete rupturing of it he does with his departure signifies how little else matters to the postmaster but his own wishes and his own sense of self. The postmaster's dismissive reaction to Ratan coming with him also helps to substantiate this. When the postmaster considers Ratan's pain for a moment, he rationalizes it and dismisses it away as something that is part of nature. In doing so, Tagore makes it clear that the entire relationship that he shared with Ratan was more for his own benefit, something that he no longer needs from her with news of his relocation.
The Postmaster is lonely in this isolated village. He begins taking an interest in the orphan girl called Ratan who lives with him and does his housework. The author does not specify the girl's age, but he calls her "a simple little girl." The reader would probably imagine that she was about ten years old. He is educated and belongs to a higher caste. She is an ignorant orphan without friends, relatives, or money; as such she belongs to the lowest caste. The two form a friendship because they are both lonely. They get to know each other by sharing their memories. She becomes strongly attached to the Postmaster and begins to think of herself as a member of his family.
On some evenings, seated at his desk in the corner of the big empty shed, the postmaster too would call up memories of his own home, of his mother and his sister, of those for whom in his exile his heart was sad,—memories which were always haunting him, but which he could not talk about with the men of the factory, though he found himself naturally recalling them aloud in the presence of the simple little girl. And so it came about that the girl would allude to his people as mother, brother, and sister, as if she had known them all her life. In fact, she had a complete picture of each one of them painted in her little heart.
A crisis comes when he falls seriously ill. Ratan spends all her time and energy nursing him back to health. But his illness has made him hate this unhealthy climate, and he decides to give up his job and return home. When he tells the little orphan girl that he is leaving and never coming back, she quite naively asks:
"Dada, will you take me to your home?"
The postmaster laughed. "What an idea!" said he; but he did not think it necessary to explain to the girl wherein lay the absurdity.
Ratan is utterly crushed by his rejection and his laughter. He means so much more to her than she ever meant to him. He considers her request absurd because, for one thing, she belongs to a lower class. But it would seem very strange for a young man like himself to be bringing home a girl who would soon be old enough to marry. There would be no place for her in his family home. His parents would never understand how he could have become so friendly with such an outcast. She belonged in the village and in the post office. He could come and go as he pleased, but she was rooted in one impoverished environment.
The Postmaster was not entirely indifferent to the feelings of Ratan. He feels guilty for abandoning her, especially since she had saved his life.
At one time he had an impulse to go back, and bring away along with him that lonesome waif, forsaken of the world. But the wind had just filled the sails, the boat had got well into the middle of the turbulent current, and already the village was left behind, and its outlying burning-ground came in sight.
The prominent Indian film director Satyajit Ray, best known in America for his wonderful trilogy The World of Apu, made a beautiful adaptation of Tagore's story in 1961. It is available on DVD under the title Two Daughters.