And within a year of their marriage she developed the “sickliness” which had since made her notable even in a community rich in pathological instances. When she came to take care of his mother she had seemed to Ethan like the very genius of health, but he soon saw that her skill as a nurse had been acquired by the absorbed observation of her own symptoms. 
Then she too fell silent. Perhaps it was the inevitable effect of life on the farm, or perhaps, as she sometimes said, it was because Ethan “never listened.” The charge was not wholly unfounded. When she spoke it was only to complain, and to complain of things not in his power to remedy; and to check a tendency to impatient retort he had first formed the habit of not answering her, and finally of thinking of other things while she talked. Of late, however, since he had reasons for observing her more closely, her silence had begun to trouble him. He recalled his mother’s growing taciturnity, and wondered if Zeena were also turning “queer.” Women did, he knew. Zeena, who had at her fingers’ ends the pathological chart of the whole region, had cited many cases of the kind while she was nursing his mother; and he himself knew of certain lonely farm-houses in the neighbourhood where stricken creatures pined, and of others where sudden tragedy had come of their presence. At times, looking at Zeena’s shut face, he felt the chill of such forebodings. At other times her silence seemed deliberately assumed to conceal far- reaching intentions, mysterious conclusions drawn from suspicions and resentments impossible to guess. That supposition was even more disturbing than the other; and it was the one which had come to him the night before, when he had seen her standing in the kitchen door. 
Now her departure for Bettsbridge had once more eased his mind, and all his thoughts were on the prospect of his evening with Mattie. Only one thing weighed on him, and that was his having told Zeena that he was to receive cash for the lumber. He foresaw so clearly the consequences of this imprudence that with considerable reluctance he decided to ask Andrew Hale for a small advance on his load. 
When Ethan drove into Hale’s yard the builder was just getting out of his sleigh. 
“Hello, Ethe!” he said. “This comes handy.” 

The previous text belongs to a scene in the fourth chapter referred to Ethan’s reflection about his marriage with Zeena. 
When they firstly met Zeena seemed to be “the genius of health”, so the concept of illness was far from her, but  within a year of their marriage she developed the sickness after her own observation of the symptoms… Soon she also started to stop talking, maybe because, as the intellingent reader should remember,  during the novel she said that Ethan “never listened” to her. To tell the truth, Ethan’s behavior is absolutely understanding, beacuse when Zeena spoke it was only to complain, so he soon acquired the habit of not answering her. Expressions like “…complain of things not in his power to remedy” reinforce Ethan’s attitude and underline his estrangement from Zeena. So there is a deep contrast between Zeena and Ethan even if they both aren’t satisfied about their marriage.
Anyway, paradoxically, her silence begun to trouble him beacuse he remembered about his mother’s taciturnity, but he was so confused because at times, looking at Zeena’s face, he felt the chill of forebodings but at other times her  silence’s reasons seemed impossible to guess and understand. 
Afer these confusing thoughts Ethan returned to reality and he felt at ease again thinking about the prospect of his evening with Mattie, even if he felt guilty for having told a lie to his wife. So Ethan’s insicurity and especially his incapacity of making a decision on his own are highlighted by the narrator. Feeling a little guilty and undecided for the situation Ethan himself decided to ask Andrew Hale for a small advance.