Below the platform, as I have said, the ground fell rapidly away to the level of the pool, which owing to rain on the hills was running very high, and, streaked with lines of greyish bubbles, poured down in amazing and ear-filling volume. But directly underneath the steep escarpment of rock on the far side of the pool it lay foamless and black, a still backwater of great depth. Above the altar-like erection again the ground rose up seven rough-hewn steps to the gate itself, on each side of which, to the height of about four feet, ran the circular wall of the castle. Inside again were the remains of partition walls between the three chambers, and it was in the one nearest to the river gate that we determined to conceal ourselves that night. From there, should the witch and Sandy keep tryst at the altar, any sound of movement would reach us, and through the aperture of the gate itself we could see, concealed in the shadow of the wall, whatever took place at the altar or down below at the pool. The lodge, finally, was but a short ten minutes away, if one went in the direct line, so that by starting at a quarter to twelve that night, we could enter the Picts’ Castle by the gate away from the river, thus not betraying our presence to those who might be waiting for the moment when the moon should shine through the lancet window in the wall of rock on to the altar in front of the river gate. Night fell very still and windless, and when not long before midnight we let ourselves silently out of the lodge, though to the east the sky was clear, a black continent of cloud was creeping up from the west, and had now nearly reached the zenith. Out of the remote fringes of it occasional lightning winked, and the growl of very distant thunder sounded drowsily at long intervals after. But it seemed to me as if another storm hung over our heads, ready every moment to burst, for the oppression in the air was of a far heavier quality than so distant a disturbance could have accounted for. To the east, however, the sky was still luminously clear; the curiously hard edges of the western cloud were star-embroidered, and by the dove-coloured light in the east it was evident that the moonrise over the moor was imminent. And though I did not in my heart believe that our expedition would end in anything but yawns, I was conscious of an extreme tension and rawness of nerves, which I set down to the thunder-charged air.