The detective stepped to the terrace door, opened it, and then quietly proceeded to try the Doctor’s keys in the lock.  Thus located he was out of visual range, and Wells took advantage of it at once.  He moved swiftly toward the fireplace, extracting the missing piece of blue-print from an inside pocket as he did so.  The secret the blue-print guarded was already graven on his mind in indelible characters—­now he would destroy all evidence that it had ever been in his possession and bluff through the rest of the situation as best he might.

He threw the paper toward the flames with a nervous gesture of relief.  But for once his cunning failed—­the throw was too hurried to be sure and the light scrap of paper wavered and settled to the floor just outside the fireplace.  The Doctor swore noiselessly and stooped to pick it up and make sure of its destruction.  But he was not quick enough.  Through the window the detective had seen the incident, and the next moment the Doctor heard his voice bark behind him.  He turned, and stared at the leveled muzzle of Anderson’s revolver.

“Hands up and stand back!” he commanded.

As he did so Anderson picked up the paper and a sardonic smile crossed his face as his eyes took in the significance of the print.  He laid his revolver down on the table where he could snatch it up again at a moment’s notice.

“Behind a fireplace, eh?” he muttered.  “What fireplace?  In what room?”

“I won’t tell you!” The Doctor’s voice was sullen.  He inched, gingerly, cautiously, toward the other side of the table.

“All right—­I’ll find it, you know.”  The detective’s eyes turned swiftly back to the blue-print.  Experience should have taught him never to underrate an adversary, even of the Doctor’s caliber, but long familiarity with danger can make the shrewdest careless.  For a moment, as he bent over the paper again, he was off guard.

The Doctor seized the moment with a savage promptitude and sprang.  There followed a silent, furious struggle between the two.  Under normal circumstances Anderson would have been the stronger and quicker, but the Doctor fought with an added strength of despair and his initial leap had pinioned the detective’s arms behind him.  Now the detective shook one hand free and snatched at the revolver —­in vain—­for the Doctor, with a groan of desperation, struck at his hand as its fingers were about to close on the smooth butt and the revolver skidded from the table to the floor.  With a sudden terrible movement he pinioned both the detective’s arms behind him again and reached for the telephone.  Its heavy base descended on the back of the detective’s head with stunning force.  The next moment the battle was ended and the Doctor, panting with exhaustion, held the limp form of an unconscious man in his arms.