Having arrived at these conclusions, Stanley found himself committed to one of two courses of action: either to play the spy on the movements of his friends, or to effect the opening of the door with the silver nails. The first was repugnant to his spirit as a gentleman, and he instantly chose the second, believing that within the portal lay the only real clue he had so far obtained. This plan also had the added recommendation of placing in his hand evidence which would not involve the introduction of Miss Fitzgerald's name in the matter. Having thus mapped out his course of action, and finding there was still an hour before lunch, he descended to the lawn, and made a preliminary inspection of the exterior walls of the old manor house. It might be possible to enter in some other way than by the oaken door which remained so obstinately closed. The building was of stone, and two stories in height, though most irregular in form, having been added to and altered during succeeding generations, as suited the taste of the owner of the period. The north-east end, however, instead of having a corner, was slightly rounded, and above the level of the roof assumed the shape of a circular tower, rising some forty feet higher than the rest of the structure, and surmounted by crumbling battlements. Even an inexperienced eye might detect that the door with the silver nails gave entrance to this tower, which Stanley was sure did not assume, in the lower storey at least, a space commensurate with its diameter above. Probably the door communicated with a narrow winding stair for the first, and perhaps the second, floors, the real space of the structure being contained in the portion which arose detached. This conjecture could easily be verified by measuring. At the first convenient opportunity he determined to make these preliminary investigations. It was said that the tower possessed no windows, and certainly this was the case, unless they gave on the leads; for, from the ground, it presented everywhere a blank wall of solid masonry, to which here and there strands of ivy clung. "But they must have got their light from somewhere," he said to himself. "Perhaps from the roof, in which case there is probably some antique form of scuttle by which entrance could be had. If one could only get up there to see--but it's not a likely place for climbing. There should be the remains of an old flag-staff or cresset, or something of that nature----" and he walked slowly backwards across the lawn, hoping to reduce the visual angle sufficiently to see any slight projection above the battlements, but in vain; and he was about to abandon his backward course and return to the house, when a soft voice murmured at his elbow:-- "Star-gazing by daylight?" and he turned, to find himself close beside Madame Darcy. "Oh, good-morning," he said, lifting his hat. "I beg your pardon, but I was trying to discover the remains of some superstructure on those battlements."