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.
"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?"
"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.
"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.