Now she took the sword back into her hand and knelt on the rim of the invisible blackness below. She had gone this path once before and once only, and never thought to find any necessity in life strong enough to drive her down again. The way was the strangest she had ever known. There was, she thought, no such passage in all the world save here. It had not been built for human feet to travel. It had not been built for feet at all. It was a narrow, polished shaft that cork-screwed round and round. A snake might have slipped in it and gone shooting down, round and round in dizzy circles-but no snake on earth was big enough to fill that shaft. No human travelers had worn the sides of the spiral so smooth, and she did not care to speculate on what creatures had polished it so, through what ages of passage.