He formed in his mind the general aspect of the house: its width faced the orange grove, the stair mounted on the hall's right, in back of which a door gave to the billiard room; on the left was the chamber of the lamp, and that, he had seen, opened into a room behind, while the kitchen wing, carried to a chamber above, had been obviously added. It was probable that he would find the same general arrangement on the second floor. The hall would be smaller; a space inclosed for a bath; and a means of ascent to the roof. John Woolfolk mounted the stair quickly and as silently as possible, placing his feet squarely on the body of the steps. At the top the handrail disappeared; and, with his back to a plaster wall, he moved until he encountered a closed door. That interior was above the billiard room; it was on the opposite floor he had heard the footfall, and he was certain that no one had crossed the hall or closed a door. He continued, following the dank wall. At places the plaster had fallen, and his fingers encountered the bare skeleton of the house. Farther on he narrowly escaped knocking down a heavily framed picture--another, he thought, of Lichfield Stope's mezzotints--but he caught it, left it hanging crazily awry. He passed an open door, recognized the bathroom from the flat odor of chlorides, reached an angle of the wall and proceeded with renewed caution. Next he encountered the cold panes of a window and then found the entrance to the room above the kitchen. He stopped--it was barely possible that the sound he heard had echoed from here. He revolved the wisdom of a match, but--he had progressed very well so far--decided negatively. One aspect of the situation troubled him greatly--the absence of any sound or warning from Millie. It was highly improbable that his entrance to the house had been unnoticed. The contrary was probable--that his sudden appearance had driven Nicholas above. Woolfolk started forward more hurriedly, urged by his increasing apprehension, when his foot went into the opening of a depressed step and flung him sharply forward. In his instinctive effort to avoid falling the pistol dropped clattering into the darkness. A sudden choked cry sounded beside him, and a heavy, enveloping body fell on his back. This sent him reeling against the wall, where he felt the muscles of an unwieldly arm tighten about his neck. John Woolfolk threw himself back, when a wrist heavily struck his shoulder and a jarring blow fell upon the wall. The hand, he knew, had held a knife, for he could feel it groping desperately over the plaster, and he put all his strength into an effort to drag his assailant into the middle of the floor.