The Abbess of Vlaye by Stanley J. Weyman

Had Bonne de Villeneuve, a day earlier, paid a visit much in fashion at that time, and consulted the "dark man" who, in an upper room on the wall of Angouleme, followed the stars and cast horoscopes, and was reputed to have foretold the death of the first Duke of Joyeuse as that nobleman passed southwards to the field of Coutras, she might have put faith in such of the events of the night as the magic crystal showed her; until it came to mirror, faint as an evening mist beside the river, her thoughts after the event. Then, had it foretold that, as she lay quaking in her bed, she would be thinking neither of the brother, whose desperate venture wrung her heart, nor of Roger, her dearer self, but of a stranger -- a stranger, whose name she had not known six hours, and of whose past she knew nothing, she would have paused, refusing credence. She would have smiled at the phantasm of the impossible.

Yet so it was. Into the quiet pool of her maiden heart had fallen in an hour the stone that sooner or later troubles the sweet waters. As she lay thinking with wide-open eyes, her mind, which should have been employed with her brother's peril, or her own escape, or her father's rage, was busy with the stranger who had dropped so suddenly into her life, and had begun on the instant to play a sovereign part. She recalled his aspect as he looked in on them, cool and confident, at their midnight conference. She heard his tone as he baffled her father's questions with cunning answers. She marvelled at the wit that in the last pinch had saved her from discovery. He seemed to her a man of the world such as had not hitherto come within the range of her experience. Was he also the perfect knight of whom she had not been woman if she had not dreamed?