But who could it be? As far as he knew, no one but Helen, Doctor Bimble and himself was aware of the existence of the revolving door, and the tunnel. It did not seem likely that anyone should be searching at random for an opening. And who could be prowling about the Gage house at such an hour? Again he put his ear to the frame. The tapping had ceased, but now he heard another and different sound that caused him to quiver with excitement. A slight metallic noise, like that produced by the contact of two objects of steel, told him that the person on the inside had found the nail.
In a twinkling he had forgotten his cramped position, the dank air and the sickening smell of moist earth. All his senses were centered on the sounds coming from the other side, so slight that his keen ears could scarcely detect them. Something told him that in a few minutes he would make a discovery of tremendous importance in relation to the Gage murder mystery. Everything depended upon whether the person on the other side would give the nail the proper twist.
Minutes dragged by on leaden feet. The Phantom felt his heart pound chokingly against his ribs, its loud beats almost drowning the slight metallic sounds coming from the other side. After what seemed hours of nerve-racking suspense, a sharp and sudden click caused him to start violently, and he almost lost his insecure footing.
Then the window frame began to turn. A glare of light struck his eyes as the opening wedge widened. With great, eager gulps he drank in the air coming from the aperture. A minute passed, and then a face, strained and ashen, was thrust into the opening.
It was Mrs. Trippe, the housekeeper. For an instant she stared into the Phantom’s startled eyes.
“He’s killing me!” she cried. “He’s afraid I’ll tell! He locked me in——”
She jerked her head to one side. Slight though she was, she almost filled the narrow opening, and he could see only a small strip of the room at her back. Suddenly a shiver coursed down her spine. A hand was projected beyond the wall, and he caught a glimpse of steel flashing in the light. Then, in quick succession, came a scream and a thud, and the woman slid from the window sill.
It had happened so quickly that the Phantom had not time to utter a word or raise a hand. Now, before he could move a muscle, the window frame slammed shut. He heard a click, signifying that the frame was caught in the steel clutches of the mechanism. He pressed his shoulders against it, but to no avail, and he knew from his previous attempt that the effort was useless. Filled with horror at what he had just seen, he slid down the incline between the walls and began to work back toward the cellar.
Finally, after endless jerks and twistings, he reached the end of the tunnel—and there a fresh shock awaited him. His feet brought up against a solid obstruction. Shove against it as he might, the little door would not yield to his frenzied pressure. For a little he laid still on his back, thinking. His mind was heavy and his thoughts flitted about in circles, but finally it came to him that while he was at the other end of the tunnel someone must have placed a heavy weight against the door.
He was trapped.