He hurried on in silence, Colton following in puzzled expectation. At the top of a mound they stopped, and were almost swept off their feet by a furious gust of wind which died down, only to be succeeded by a second, hardly less violent. In a glare of lightning that spread across the south, Colton saw the fretted waters of a little lake below them. “We’re going to get that storm, I think,” he said. No reply came from his companion. In silence they stood, for perhaps ten or fifteen minutes. Then the wind dropped temporarily. Colton was wondering whether courtesy to the peculiar individual who had haled him forth on this errand of darkness was going to cost him a wetting, when the wind dropped and the night fell silent. “There! Did you hear it?” the professor exclaimed suddenly. Colton had heard, and now he heard again, a strange sound, from overhead and seeming to come from a considerable distance; faintly harsh, and strident, with a metallic sonance. “Almost overhead and to the west, was it not?” pursued the other. “Watch there for the lightning flash.” The lightning came, in one of those broad, sheetlike flickers that seem to irradiate the world for countable seconds. Professor Ravenden’s arm shot out. “Did you see?” he cried. Darkness fell as the query was completed. “I saw nothing,” replied Colton. “Did you? What did you see?” A clap of wind blew away the reply, if there was any. This time the wind rose steadily. They waited another quarter of an hour, the gale blowing without pause. “This is profitless,” said Professor Eavenden, at length. “We had best go home.” Thankful for the respite, the younger man rose from the little depression where he had crouched for shelter from the wind. With a thrill of surprised delight, he realised that he was healthily sleepy. The quick, hard walk, the unwonted exercise, and the soft, fresh sweetness of the air, had produced an anodyne effect. But was the air so sweet? Colton turned and sniffed up wind. “Do you smell anything peculiar?” he asked his companion. “Unfortunately I am troubled with a catarrh which deadens my sense of smell,” replied the scientist. “There’s a peculiar reek in the air. I caught it with that last shift of wind. It’s like something I’ve come across before. There!” “Can you not describe it?” “Why, it’s—it’s a sickish, acid sort of odour,” said Colton hesitantly. “Where have I—— Oh, well, it’s probably a dead animal up to windward.” As they reached the house, he turned to the other. “What was it you thought you saw?” he asked bluntly. “What are you looking for?” “I am not satisfied that I saw anything,” answered Professor Ravenden evasively. “Imagination is a powerful factor, when the eye must accomplish its search in the instantaneous revelation of a lightning flash. As for what I am seeking, you heard as much as I. I thank you for your help, and, if you will pardon me, I will bid you good-night here, as I wish to make a few notes before retiring.”