What is the topic and the context of this quote in Jane Eyre?

The quote is : “What crime was this that lived incarnate in this sequestered mansion, and could neither be expelled nor subdued by the owner?—what mystery, that broke out now in fire and now in blood, at the deadest hours of night? What creature was it that masked in an ordinary woman’s face and shape uttered the voice, now of a mocking demon, and anon of a carrion-seeking bird of prey?” (210)