 At the same time they quickened the throb of his headache, and this reminded him that he had been drugged. He was just formulating to himself the theory that the stuff they had given him might have some effect on the pupil and that this would explain the unnatural splendour and fullness of the sky, when a disturbance of silver light, almost a pale and miniature sunrise, at one corner of the skylight, drew his eyes upward again.