In the light of the candles, all could see that, except for the little space into which he had fallen, the whole interior of the tower was filled by a narrow stone staircase, which, in its ascent, half turned upon itself. Of the missing document, however, there was not a trace. The stillness in the great hall was oppressive. Even their own footsteps on the stones seemed, to the hearers, preternaturally loud. Mr. Riddle raised the sconce above his head, and there burst on a sudden a shimmering flash of a thousand prismatic colours from the head of the staircase. He fell back a step, as did the others, and Kingsland murmured in awe-struck tones:-- "What's that?" Riddle again raised the sconce, and again the burst of light from the head of the stairs overwhelmed him, but this time he stood his ground. "What is it?" asked Kent-Lauriston. "I don't know." "Let us examine." "As far as I can make out, it's a flexible curtain of chain mail--hung across the staircase." "I swear it moved," said the Lieutenant. "No, it was the light which moved," replied the discoverer. "You see," and he swayed the sconce from side to side, making the curtain appear to be moving silently. "If I take the light away," he continued, "there's nothing to be seen;" and he removed the sconce, leaving only the black mass of the steel curtain visible. "Nothing to be seen--isn't there? Look there!" whispered Kingsland, and, following the direction of his eyes, the others saw a broad band of blood-red light steal out of the blackness, across the steps at the head of the staircase. "That room has been closed for centuries, and yet there is a light burning," he continued hoarsely. "Shut the door, my dear fellow, and let's get away." "It merely confirms another theory of mine," said Riddle, "which is, that, as there are no windows on the outside of the tower, they must have got their light and ventilation from the roof. I think it's fair to suppose that they used red glass, and that the full moon is shining through it." "Then you can go and prove it if you like, but if you take my advice, you'd better leave it alone." "I don't like, my dear Kingsland, though I'm going, just the same. I daresay I shall find something very nasty at the head of the stairs, but it won't be supernatural. If I want you, I'll call you. If not, wait till I come back." Putting down the sconce, he slipped off his dress coat, and crossing the hall, picked up a stout hunting crop, the property of the Lieutenant, while his two companions stood staring at the blood-red band of light which lay across the steps, and which seemed to their excited imagination to grow broader and deeper. "What do you think he'll find up there?" asked Kingsland. Kent-Lauriston shrugged his shoulders.