Nan proceeded to cross the narrow ridge. She was particularly surefooted as a rule, her supple body balancing itself instinctively. But to-day, for the first time, she felt suddenly nervous as she neared the crag and, glancing downward, caught sight of the sullen billows thundering far below on either side. Perhaps the events of the day had frayed her nerves more than she knew. It was only by an effort that she dismissed the unaccustomed sensation of malaise which had assailed her and determinedly began the ascent to the castle by way of a series of primitively rough-hewn steps. They were slippery and uneven, worn and polished by the tread of the many feet which had ascended and descended them, and guarded only by a light hand-rail that seemed almost to quiver in her grasp as, gripped by another unexpected rush of fear, Nan caught at it in feverish haste. She stood quite still--suddenly panic-stricken. Here, half-way up the side of the steep promontory, the whole immensity of the surrounding height and depth came upon her in a terrifying flash of realisation. From below rose the reiterated boom of the baulked waves, each thud against the base of the great crag seeming to shake her whole being, while, whichever way she looked, menacing headlands towered stark and pitiless above the sea. She felt like a fly on the wall of some abysmal depth--only without the fly's powers of adhesion. Very carefully she twisted her body sideways, intending to retrace her steps, but in an instant the sight of the surging waters--miles and miles below, as it seemed--sent her crouching to the ground. She could not go back! She felt as though her limbs were paralysed, and she knew that if she attempted to descend some incalculable force would drive her straight over the edge, hurtling helplessly to the foot of those rugged cliffs. For a moment she closed her eyes. Only by dogged force of will could she even retain her present position, half crouching, half lying on the ill-matched steps. It almost seemed as though some power were drawing her, compelling her to relax her muscles and slide down, down into those awful depths. Then the memory of a half-caught phrase she had overheard flashed across her mind: "If you feel giddy, always look up, not down." As though in obedience to some inner voice, she opened her eyes and looked up to where, only a few battered steps above, she could see the door of the castle. If she could only make it! Rising cautiously to her knees she crawled up one more step and rested a moment, digging her fingers into the crevices of the rock and finding a precarious foothold against a projecting ledge. Keeping her eyes fixed upon the door she scrambled up a few inches further, then paused again, exhausted with the strain.