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.