The Familiar by Joseph Thomas Sheridan Le Fanu

IT was not to be expected that Captain Barton's changed and eccentric habits should long escape remark and discussion. Various were the theories suggested to account for it. Some attributed the alteration to the pressure of secret pecuniary embarrassments; others to a repugnance to fulfil an engagement into which he was presumed to have too precipitately entered; and others, again, to the supposed incipiency of mental disease, which latter, indeed, was the most plausible, as well as the most generally received, of the hypotheses circulated in the gossip of the day.

From the very commencement of this change, at first so gradual in its advances, Miss Montague had of course been aware of it. The intimacy involved in their peculiar relation, as well as the near interest which it inspired, afforded, in her case, a like opportunity and motive for the successful exercise of that keen and penetrating observation peculiar to her sex.