Sentence:  [H]e would sit over the fire with a book in his hand, staring over it into the red glow with his brows knit, and a dogged, almost sullen look about his mouth. [...] One evening about this time Mrs. Gray, who was a woman of determination, and who had a horror of what she called 'the <WSD>doldrums</WSD>,' made up her mind that she had had enough of this kind of thing, and must come to the bottom of this affliction, or temper, or money embarrassment of her son's without further delay. 
Meaning of the word marked with <WSD> tags:  "Usually preceded by" '''(the)''': a state of apathy or lack of interest; a situation where one feels boredom, ennui, or tedium; a state of listlessness or malaise.