her confederate. He waited patiently until the waning afternoon light told him that it was time to begin his watch before the house at number 162.
Across the street a residence, closed for the summer, its front entrance boarded up, afforded him a convenient place to wait. He sat down upon the steps, and pretended to be occupied with a newspaper. His eyes, however, sought constantly the doorway opposite.
A number of persons entered the place, during the next two hours, but Marcia Ford was not amongst them. As the darkness began to approach, and lights in the streets and houses flared up, Duvall rose, crossed the street, and stationed himself at a nearer point, from which he might the more certainly identify anyone entering the house. Miss Ford, however, failed to appear.
From the sign in the window, to the effect that roomers were wanted, Duvall concluded that the Ford girl did not take her meals in the house. His watch showed him that it was nearly seven. Doubtless she had arranged to dine before returning home. In a flash it came to him that his opportunity to make an examination of her room was now at hand.
To secure entrance to the room by the usual channels was clearly out of the question. The people at the boarding house would, of course, not permit it. But could he discover the means of communication, whatever they were, between Miss Morton's apartment and the girl's room, he might be able to enter the latter unknown and unobserved. He had thought of attempting this during the afternoon, but realized that he could not hope to accomplish it, in broad daylight, without being seen by the occupants of the neighboring buildings, and perhaps arrested as a burglar or sneak thief.
With a last glance down the street, he hastened back to the apartment building and made his way to Mrs. Morton's flat. Passing quickly through Ruth Morton's bedroom, he climbed out upon the fire escape and looked about.
Below him were the rear yards of the houses fronting on the next street. To the right he could see the bulk of the apartment building, blocking his view of the avenue beyond. To the left were the rear buildings of the adjoining houses. It was quite dark, the sky was starless, but all about him gleamed the lights in the windows of the neighboring buildings.
Neither to the right, nor to the left was there any possible way by which access to the point where he now stood could be gained. From below, it was possible, although his previous examination had showed him both the fact that the newly painted surface of the fire escape was unmarred, and that the ladder at the lower floor was drawn up some nine or ten feet from the ground. He felt certain that Miss Ford had not reached Ruth's room in that way.
He glanced upward. The fire escaped stopped at the level of the floor above. To ascend from it to the roof was impossible.
Remembering that the top apartment was vacant, Duvall re-entered the building and hunting up the janitor, told him that he desired to get out on the roof.
The man remembered him, from his first visit, and the inquiries he had then made about the tenants of the apartment above.
"I am making some special inquiries on Mrs. Morton's behalf," he explained. "You can go with me, if you like, to see that I do nothing I shouldn't."
The janitor joined in his laugh.
"I'm not worrying," he rejoined, "but I'll go along, just the same, to show you the way." He led the detective up one flight of stairs and, going to the end of the outer hall, unlocked and opened a small door beside the elevator shaft. A short spiral staircase was disclosed.
Snapping on an electric light, the man ascended the steps, and, after fumbling for a moment with the catch, threw open a trapdoor leading to the roof. In a moment both he and Duvall had climbed out upon the tiled surface. Duvall went to the edge which overlooked the house adjoining, and peered down. He at once saw something that interested him.
The house with the dormer windows consisted, as has been previously mentioned, of four stories and an attic. Its roof rose several feet above the level of the window of Ruth's room, which was on the fourth floor of the apartment building. But Duvall saw at once that this elevation of the adjoining house did not extend all the way back, but, in fact, stopped a little beyond the point where it joined the apartment. From here to the rear of the lot the building had no attic, its rear extension being but four stories high. In this position on the apartment-house roof, the roof of the back building was at least fifteen feet below him.
Another thing that he noticed at once was the fact that the second house, No. 162, was of almost the same design as the first, that is, it consisted of a main building with an attic, and a rear extension, reaching to the same level as that of the house between. It was clear that if anyone living in the second house could obtain access to the roof of the back building, he would be able to walk across that of the first or adjoining house, and reach a point directly beneath where he stood.
But, granting the possibility of this, of what use would it be? A person on the roof below him would in no conceivable way be able to reach either of the windows of Ruth Morton's room. Was it possible that an opening had been made through the wall of the apartment building itself? He thought it unlikely, but determined to investigate.
"I must get down on that roof below," he informed his companion. The janitor grinned.
"How are you going to do it?" he asked.
"Haven't you a ladder—a rope?"
The man thought a moment.
"I've got a short ladder in the cellar, only about eight feet long, I guess. I'm afraid it would not do."
"Yes it would," replied Duvall, pointing to the roof of the attic portion of the house below. "I'll get down to the roof of the main part of the house first, and from there to the roof of the back building. An eight-foot ladder will be long enough for that. Bring it up, will you?"
The man hesitated.
"I don't just like this idea of going on other people's roofs," he said.
"You don't need to go. I've got to. I'm a detective, and I'm working for Mrs. Morton on a most important case." As he spoke, he took a bill from his pocket and pressed it into the man's hand.
The janitor responded at once.
"I'll fetch it up, sir," he said. "Wait for me here."
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
