The third man they almost carried into the room between them. He was tall and broad-shouldered, and he was so roped from his shoulders to his knees that he could only move in steps of an inch at a time unaided. His face was divided into two parts by a black wooden ruler, which had been forced into his mouth as a gag, and which was held in position by cords attached to the ends, which passed round the back of his head.

"Does that induce you to stay?" asked Raxel.

"I think it means that I am induced to go out at once, and find a policeman," said the girl, and took two steps towards the door.

"Wait!"

Raxel's voice brought her to a stop. The command in it was so impelling that for a moment it was able to overcome the panicky desire for flight which was rapidly getting her in its grip.

"Well?" she asked, as evenly as she could.

"You are a chemist, Miss Tregarth," said Raxel, "and therefore you will be familiar with the properties of the drug known as bhang. The cigarette you half-smoked was impregnated with a highly concentrated and deodorized preparation of bhang. According to my calculations, the drug will take effect about now. You still have the automatic I gave you in your hand, and there, in front of you, is a man gagged and bound. Stand away, you two!"

The Professor's voice suddenly cracked out the order with a startling intenseness, and the two men who had stood on either side of the prisoner hurried into the opposite corner of the room and left him standing alone.

Betty Tregarth stared stupidly at the gleaming weapon in her hand, and looked from it to the bound man who stood stiffly erect by the door.

Then something seemed to snap in her brain, and everything went black; but through the whirling, humming kaleidoscope of spangled darkness that swallowed up consciousness, she heard a thousand miles away, the report of an automatic, that echoed and reechoed deliriously through an eternity of empty blackness.