It did leave me wondering whether Walter, Constance’s husband, had any idea.

I couldn't tell at all. There was the quotation from early in Katherine and Constance's relationship: "my dearest brother, I must beg of you not to discourse to any other what you know passes betwine Mrs. Thimelby and me; for no creature, but your selfe who knowes all my hart, dare I reveale any of this to, least exceptience be taken." But I also feel like after twenty years, a person notices something?