How should it be? he thought. Should he contrive a boating party upon the great lake? Boats had before now been upset, and their occupants drowned. Such accidents were not at all uncommon. Or there might be some terrible catastrophe with the spirited horses of the carriage; the part of the Castle where her ladyship slept might catch fire at a time when a hampered lock and fastened window precluded escape; or, better still, there was poison! The evil spirit must at that time have had full possession of the citadel, for it was with a baleful glare in his eyes that Sir Murray Gernon strode up and down his room, stepping softly, as if fearing to interrupt the current of his thoughts--thoughts that, in his madness, seemed to refresh the thirsty aridity of his soul. After all these months of misery, had at last, then, come the solution of his difficulty? and he laughed--and laughed savagely--as he sat down once more to plan. Mercy? What had he to do with mercy? What mercy had they had upon his life? Had they not blighted it when he was a calm, trusting, loving man, searing his spirit with something more burning and corroding than the hottest iron--the sharpest acid? Let them seek for mercy elsewhere: his duty was to dispense justice, and he would be just! Who could gainsay it? Was it not written in the Book that the punishment for the crime was death--that the sinners should be stoned with stones until they died? Not that he would stone them: his should be a quiet, insidious vengeance--one that the world should not suspect, and he would plot it out in time. But what if she were, after all, innocent? He tore that thought from his heart, accusing himself of cowardice, and of seeking a way out of what would be the path to a new life. No; there was no innocence there. His would be a crusade against guilt; and he vowed a fearful vow that he would carry out his vengeance to the end. Should it be by poison? "Tap! tap! tap!" Three distinct, sharp touches as of a nail upon the window-pane made Sir Murray start, shivering, from his guilty reverie. What was that? Some ghostly warning for or against his plots?--or was he so distempered by his broodings that this was but the coining of imagination? "_Tap! tap! tap_!" There it was again, and for a moment a strange sense of terror pervaded him, and he could not stir. But only for a moment; the next minute a feeling of grim satisfaction prevailed. This, then, was to be a night of enlightenment--here was a new revelation--this, then, was the means of communication? Evidently some mistake of the bearer, and he had but to go to the window, stretch forth his hand, and take a letter; or--the thought sent a thrill through him as he stepped forward--was it the keeping of an assignation? The window was many feet above the ground, and if he dashed back the ladder--