Had he been inclined to doubt it, two photographs upon the wall would have convinced him. One was a picture of the Ford girl herself. The other was a portrait of the woman of the cab, the one that Duvall fully believed to be the author of the attacks upon Ruth Morton.

He examined the various articles about the room with the utmost care, but nothing of any interest rewarded his search. It had been his hope that he might find something of definite value—the typewriter, perhaps, upon which the threatening letters had been written, the black sealing wax, used in making the death's-head seals, the paper employed by the writer. None of these things was in evidence; there was no typewriter, the table contained a small bottle of ink, a couple of pens, and some cheap envelopes and a writing tablet of linen paper quite different from that upon which the warning letters had been written. There was nothing, absolutely nothing, in the place to connect its occupant with the sending of the letters, except the room's location, in such close proximity to that of Ruth Morton, and the photograph of the woman of the cab, hanging upon the wall.

Duvall, greatly disappointed, was about to take his departure, when he observed at the far end of the room a door. Whether it led to another room, or to a bathroom, or merely to a closet, he did not, of course, know. There was danger, he fully realized, that Marcia Ford might return at any moment. There was equal danger that, upon opening the door, he might find himself in another room, possibly an occupied one. He thought at one time that he heard sounds on the far side of the door, but when he paused and stood listening he could distinguish nothing, and concluded that he had been mistaken. Shutting off the light of his pocket torch for the moment, in order that, should the entrance lead to another room, its rays might not betray his presence, Duvall grabbed the door knob, and, turning it softly, opened the door.

For a moment he had a glimpse of a black cavern, and then, with incredible swiftness, something struck him a heavy blow in the face. What it was he was too much surprised and stunned to realize. His electric lamp fell from his hand, and clattered to the floor.

Realizing his helplessness in the almost total darkness, he bent down, groping about in an unsuccessful effort to recover the searchlight. And then, with a loud cry, a heavy body projected itself upon him, grasping wildly at his hair. An arm, clothed in some silken material, encircled his throat. He felt himself choking. And at the same moment a strange and irrational terror seized him. He seemed in the grasp of something uncanny, something inhuman, in spite of its very human cries. With a shudder he sprang to his feet, unable to locate the missing electric torch, and shaking the shrieking figure from him, plunged toward the window by which he had entered. It was not alone the surprise, the nameless terror of the thing, that sent Duvall headlong from the room. He fully realized that the noise of the encounter, the shrieks of his assailant, would quickly bring the other inmates of the house to the room. He had no wish to be discovered there—his entrance had been too irregular, too illegal, for that. With extraordinary rapidity he flung himself through the window and without waiting to observe the results of his intrusion, sped swiftly across the roofs of the two buildings, up the steps to the attic roof, and from there, by means of the ladder, to the roof of the apartment building. The janitor sat where he had left him, smoking a pipe. Duvall looked back. Lights were visible in the room he had just left. He saw a figure, one that closely resembled Marcia Ford, cross the lighted area of the window. There was a second figure with her—smaller, shorter, he thought. Who—what was it that had attacked him? He stood in a daze, unable to grasp the meaning of the experience through which he had just passed.

The janitor took his pipe from his mouth and rose.

"Find what you were looking for?" he asked with a grin. Duvall shook his head.

"No," he said. "Not exactly. But I'm on the track of it."

"Want the ladder any more?"

"No, not to-night." He assisted the man to draw it up to the roof.