Duvall occupied the few moments consumed by the janitor's absence in examining, by means of his pocket electric torch, the surface of the roof on which he stood. The smooth flat terra cotta tiles showed no distinguishing marks. Here and there spots of paint, marred by footprints, indicated where the painters at work on the building had set their buckets, no doubt while painting the wooden portions of the trapdoor, and the metal chimney-pots on the roof.

The man returned in a few moments with the ladder, and Duvall, lowering it to the level of the main portion of the adjoining house, saw that it was of sufficient length to permit his descent. In a moment he had slipped off his shoes, and was cautiously descending the ladder.

Once on the surface of the main roof of the house, he had intended to take down the ladder and, by means of it, descend the remaining six or seven feet to the roof of the back building, but he found that means for this descent already existed. A rough but permanent wooden ladder led from the higher level to the lower. Duvall judged that it had been placed there to provide easy communication between the upper roof and the lower. Leaving the ladder where it stood, he made his way down to the roof of the back building. It was covered with tin, and he walked softly in his stockinged feet to avoid being overheard.

His first act was to go to the wall of the apartment house which faced him, and make a thorough examination of it by the light of his electric torch. He judged that in the position in which he now stood he was about on a level with the floor of Ruth's room. The brick wall of the apartment building facing him was blank, that is, it contained no windows. After a minute examination, Duvall was forced to the conclusion that no entrance to the girl's bedroom had been made through it. The bricks were solid, immovable, the cemented joints firm and unbroken. A moment later he turned to the left.

Here the rising wall of the attic story of the house faced him, reaching to a point above his head. Two dusty and long unopened dormer windows, similar to those facing on the court, confronted him. He remembered that the servant of the house next door had informed him, earlier in the week, that the attic was, and long had been, unoccupied.

Whether the attic was tenanted or not, however, had no bearing on the problem which confronted him. The windows might serve as a means whereby anyone could reach the roof of the back building from the house proper, but they did not suggest any means whereby anyone might reach the windows of Ruth's bedroom. And by ascending to the point on the attic roof where his ladder stood, the problem was no nearer a solution, for a person standing there was on the edge of the court between the buildings, seven feet or more above the girl's bedroom window, and as many away from it. He turned away, and approaching the rear edge of the back building, looked over.

To his left, some eight feet away, was the fire escape before the rear window of the girl's bedroom. Standing on that sharp edge, he realized that in no way could he reach the railing of the fire escape, except by jumping, a feat that an expert gymnast might have hesitated to attempt, at that height above the ground. And could it be done successfully, what about the crash, the noise which must inevitably result from such a performance? What about the damage to the paint upon the fire escape's iron surface? And yet it would seem that a young girl had accomplished this feat, without noise, without making the least mark to register her passage. He thought of the tell-tale handkerchief, which he had found on the fire escape earlier in the evening, then turned back with a feeling of annoyance. The thing was, he realized, an impossibility.

A sudden sense of the passage of time made him hurry to the roof of the rear building of the house at No. 162. Like its neighbor, it was built with an attic story, and in the rear were two dormer windows opening in the same way upon the lower roof. Could these windows, by any chance, be those of the room of Marcia Ford? It seemed highly probable, since, if she had operated from the roof, they could afford an easy way to reach it. Very cautiously he crept up to the nearer of the two windows and looked in.

The room before him was in total darkness, and the very faint radiance from without was not sufficient to enable him to distinguish anything within it. The window, however, he saw to his delight was open, and the opening, although small, was quite large enough to enable him to crawl in. Holding his electric torch in one hand, he crept into the room.

The beam of light from his torch, although powerful, was, of course, very concentrated. He swept it about the room, to make sure that it was unoccupied. It was a small room, long and narrow, with the single dormer window, by which he had just entered, at one end, and a similar one at the side, in the slanting mansard roof. It contained a small bed, a chiffonier and dresser, a table, some chairs and a trunk. It was a woman's room; one glance at the dresser told him that, and a handkerchief lying crumpled on the latter's top proved to be identical with the one he had found on the fire escape, both in its general character, and in the initial "F" in one of its borders. Beyond any doubt, he was now in Marcia Ford's room.