The young policeman, Constable Rider, walked more quickly than usual, because of the cold, but he did not consciously   neglect any part of his work. His torch flashed on doorways and windows as he looked for anything that was at all suspicious, and when he ever thought that anything was unusual, he went to try the door and window, probably unheard by the people sleeping in the room just above his head. As he turned a corner, he heard a slight rustling sound -- it might be a cat, it could even be a dog, although few dogs wandered about at night. Rider saw nothing. A cat then? Usually if you disturbed a cat, it ran off and jumped, and you heard or noticed something else. By doing a lot of night, you learned to notice these things, but now all Rider noticed was the silence which had followed the rustling sound. So he acted cautiously. He did not flash his torch about the houses near the corner but walked on, and, a little way from the spot where he heard the sound, stopped and bent his head, as if he was lighting a cigarette. A policeman who stopped to light a cigarette seemed the most unsuspicious policeman in the world. There was still no sound. There were bushes in the garden of the house where Rider had first heard it and he knew that a man could hide there out of sight. But if he went back, it would warn any such man. So instead he stood and shone his torch at the window nearest him, and as if he had noticed something unusual, he walked towards it and opened the wooden gate, which made no sound at all. He reached the entrance and shone the torch on the keyhole of the front door -- and as he did so, the rustle came again, this time much more softly. He looked round quickly. As he then heard no more sounds, Rider decided   _  .
that he had been mistaken, and walked on that he might as well have a cigarette to flash his torch on a window near the corner not to show that he had noticed anything