What did Jane find unusual about the third story?

When Mrs Fairfax shows Jane up to the third story of Thornfield Hall, Jane observes that many pieces of furniture are of older fashions, as if they had been removed to the third story once they were no longer needed lower down, which gave it a sense of being "a shrine of memory." The floor was gloomy and the rooms dark, and the hangings looked "strange" in such a way that Jane did not feel inclined to spend much time up there. Essentially, the third story had a dark and vaguely unsettling aspect, such that Jane opines to Mrs Fairfax that the third story would be were the Hall's ghost lived, if there was one. The front and back rooms of the story were even separated by a corridor whose doors were all shut as if "in some Bluebeard's castle."
Already feeling unsettled, then, Jane is very surprised to hear what she believes to be a "curious laugh." However, Mrs Fairfax assures her that it is only one of the servants.