The Professor smiled.

"You could shoot me, and no one would hear," he said. "I ask you to observe that there are no windows in this room. The walls are thick, and so is the door--the room is practically sound-proof. Certainly the report of that automatic would not be audible in the street. I can be quite positive about that because I have verified the statement by experiment."

"Then--"

"You may understand me better," said the Professor quietly, "if I tell you first of all that I intend to keep you here for a few hours."

"Really?"

She was becoming convinced that the man was mad, and somehow the thought made him for a moment seem less alarming. But there was nothing particularly insane about his precise level voice, and his manner was completely restrained. She settled back in her chair and endeavoured to appear completely unperturbed. Then she thought she saw a gleam of satisfaction light up in his eyes as she took another puff at the cigarette he had given her, and her fingers opened and dropped it suddenly as though it had been red hot.

"And I suppose the cigarette was doped?" she said shakily.

"Perhaps," said the Professor.

He rose and went quickly to a bell-push set in the wall beside the mantelpiece, and pressed it.

Betty Tregarth got to her feet feeling strangely weak.

"I make no move to stop your going," said Raxel quickly. "But I suggest that you should hear what I have to say first."

"And you'll talk just long enough to give the dope in that cigarette time to work," returned the girl. "No--I don't think I'll stay, thanks."

"Very well," said Raxel. "But if you won't listen to me, perhaps you will look at something I have to show you."

He clapped his hands twice, and the door opened. Three men came in. One was the butler who had admitted her, the other was a dark, heavy-jowled, rough-looking man in tweeds.