Once more Sir William looked round to see if Wilson Guest had returned.
The actual projecting apparatus by which the transformed light rays were thrown upon the screen required some attention. The delicate apparatus which focussed the lens of the projector, in order to bring it into the nearest possible co-ordination with the light which it had to magnify and transmit, needed some little care.
"Will you excuse me for a moment," he said to everybody there, "if I leave you in darkness again, until the man comes? I wish to attend to a portion of the mechanism here, and I can only do so by turning off the lights."
There was a chorus of "Oh, please do so, Sir William," and suddenly the laboratory was once more plunged into utter blackness.
Nobody talked much now, curiously enough. For a moment there was nothing heard but the regular beating of Lady Poole's fan, and one whispering conversation which might, or might not, have been carried on between Lord Landsend and Mrs. Hoskin-Heath.
Then the thunder, which had been quiet for a little time, began to mutter once more. The dark air became hot and full of oppression. And in the dark Lord Malvin took the hand of Marjorie Poole in his own. "Be brave," he said into her ear. "I know what you must suffer, believing what you believe."
She whispered back to him.
"I have known it ever since I have been in this place," she said. "Oh! Lord Malvin, I have known it quite certainly, Guy is in this house!"
"Donald Megbie has gone out, as you saw just now," he answered. "Be brave! be strong! I believe that God is guiding you. I too have felt the psychic influence of something strange and very, very terrible in the air of this house."
In a moment more the beginning of the end came. The great twelve-foot circle of light flashed out upon the screen, but now with an extraordinary brightness and vividness, such as the spectators had not seen before during the course of the experiments. For a space of, perhaps, ten seconds, there was no sound at all. Nobody quite realized that anything out of the ordinary was happening, except possibly the scientists, who had a complete grasp of the mechanical methods of the experiments and realized that in this room, at any rate, no one was wearing the cap.