They stood quite still, a little terrified.  In a moment or two the door reopened.  A finger turned out all the electric lights but one.  Then there was nothing to be seen but a pair of white hands, which seemed to come floating towards them through the darkness—­a pair of white hands and a pair of gleaming eyes.  Lenora screamed wildly.  Even Laura was unnerved.

“Stop that!” she cried out.  “Who are you, anyway?”

The lights were suddenly turned on.  Quest threw off his disguise.

“There you are,” he exclaimed triumphantly.  “Ingenious, but one ought to have seen through it long ago.  The stroke of genius about it was that as soon as he had used a dodge once or twice and set you thinking about it, he dropped it.”

The door was suddenly opened and French entered.

“Beaten!” he exclaimed tersely.

“You haven’t found him?” Quest asked.

French shook his head.

“We’ve searched every room, every cupboard, every scrap of the cellar in the house,” he announced.  “We’ve been into every corner of the grounds, searched all the place inside and out.  There’s no sign of the Professor.”

Quest pocketed the diary.

“You’re perfectly certain that he is not in this house or anywhere upon the premises?”

“Certain sure!” French replied.

Quest shrugged his shoulders.

“Well, we’d better get back,” he said.  “You come, too, French.  We’ll sit down and figure out some scheme for finding him.”

They made their way to the front door and crowded into the autos.  The two men left with marked reluctance.  The two girls had but one idea in their heads—­to get away, and get away quickly.

“Do start, please,” Lenora begged.  “There’s just one thing in life I want, and that is to be in my own room, to feel myself away from his world of horrible, unnatural mysteries.”

“The kid has the right idea,” Laura agreed.  “I’ve had enough myself.”

They were on the point of starting, the chauffeur with his hand upon the starting handle, French with the steering wheel of the police car already in his hand.  And then the little party seemed suddenly turned to stone.  For a few breathless seconds not one of them moved.  Out into the clammy night air came the echoes of a hideous, inhuman, blood-curdling scream.  Quest was the first to recover himself.  He leaped from his seat and rushed back across the empty hall into the study, followed a little way behind by French and the others.  An unsuspected panel door which led into the garden, stood slightly ajar.  The Professor, with his hand on the back of a chair, was staring at the fireplace, shaking as though with some horrible ague, his face distorted, his body curiously hunched-up.  He seemed suddenly to have dropped his humanity, to have fallen back into the world of some strange creatures.  He heard their footsteps, but he did not turn his head.  His hands were stretched out in front of him as though to keep away from his sight some hateful object.