“I do not think they suspect any one in particular just yet,” he replied.
“Have they no clue of any kind?”
“They have several clues of a kind. They have discovered some footprints outside the window of the room in which we sat. The window itself has been forced. And that reminds me of something else I wanted to tell you. The police have naturally questioned me in order to obtain any light I can throw on the mystery. One of the first things they asked me was how I got into the house. I told them that the door was open, and that as no one came when I knocked I walked in and sat down. I think that was what you told me you did.”
“Yes,” she replied. “The door was open.”
“You see, I forgot to fortify myself with a ready made story which would fit all these questions. The theory of the police at present is that the murderer was in the house all the time we were there.”
“Oh!” she exclaimed. It was obvious that she was deeply interested in that theory. “Because of the crash we heard?”
“Partly because of that, and partly because that strange looking document we found on the stairs has disappeared. It was gone when I went back to the house with the police sergeant. Their theory is that the murderer was in the house when I arrived—that is, when you arrived—but of course they didn’t know about your being there. As they reconstruct the tragedy, the murderer was making his way downstairs with the plan in his hand just as I—meaning you—arrived at the door. In his alarm he dropped the plan and retreated upstairs. The crash we heard was made by him knocking down a picture that hung on the wall near the top of the staircase—that is on the second floor. After we left the house he came down, found the plan in the sitting-room and made off with it.”
“To think of his being in the house all the time I was there alone!” she said. “It makes me shudder even now.”
“The police are under the impression that they will not have much difficulty in getting hold of him, but on the other hand Mr. Crewe thinks there are some puzzling mysterious features which the police have overlooked.”
“Mr. Crewe!” she exclaimed. “Do you mean the famous London detective?”