“Look here,” he said, glancing out of the corner of his eye to be sure that Laura was there, “let me show you what I have just discovered.”

He felt with his thumb for a spring.  In a moment or two a portion of the wall, about two feet in extent, slowly revolved, disclosing a small cupboard fitted with a telephone instrument.

“A telephone,” the Inspector remarked, pointing to it, “in an unoccupied house and a concealed cupboard.  What do you think of that?”

The Professor shook his head.

“Don’t ask me,” he groaned.

French took the receiver from its rest and called up the exchange.

“Inspector French speaking,” he announced.  “Kindly tell me what is the number of the telephone from which I am speaking, and who is the subscriber?”

He listened to the reply and asked another question.

“Can you tell me when this instrument was last used?...  When?...  Thank you!”

The Inspector hung up the receiver.

“The subscriber’s name,” he told them drily, “is Brown.  The number is not entered in the book, by request.  The telephone was used an hour ago from a call office, and connection was established.  That is to say that some one spoke from this telephone.”

“Then if your men have maintained their search properly, that some one,” Quest said slowly, “must be in the house at the present moment.”

“Without a doubt,” the Inspector agreed.  “I should like to suggest,” he went on, “that the two young ladies wait for us now in the automobile.  If this man turns out as desperate as he has shown himself ingenious, there may be a little trouble.”

They both protested vigorously.  Quest shrugged his shoulders.

“They must decide for themselves,” he said.  “Personally, I like Lenora, who has had less experience of such adventures, to grow accustomed to danger....  With your permission, Inspector, I am going to search the front room on the first floor before we do anything else.  I think that if you wait here I may be able to show you something directly.”

Quest ascended the stairs and entered a wholly unfurnished room on the left-hand side.  He looked for a minute contemplatively at a large but rather shallow cupboard, the door of which stood open, and tapped lightly with his forefinger upon the back part of it.  Then he withdrew a few feet and, drawing out his revolver, deliberately fired into the floor, a few inches inside.  There was a half stifled cry.  The false back suddenly swung open and a man rushed out.  Quest’s revolver covered him, but there was no necessity for its use.  Craig, smothered with dust, his face white as a piece of marble, even his jaw shaking with fear, was wholly unarmed.  He seemed, in fact, incapable of any form of resistance.  He threw himself upon his knees before Quest.

“Save me!” he begged.  “Help me to get away from this house!  You don’t belong to the police.  I’ll give you every penny I have in the world to let me go!”