“Most people,” the dog explained in an annoying instructional tone (it was pretty much how he sounded all the time), “think forwards. They think: Well, if this happens now, this is logically what will happen next. But to be a great detective, you must be able to think: If something has happened, what was the cause? Essentially, you must be able to reason backward until you arrive at the beginning.”

“Can you provide an example?” I asked, half hating myself for my own curiosity.

“What could be easier?” he said, pleased. “Take for example, Jefferson Hope. In his case, once I saw the first body and realized it had been murder, I moved in time directly backward from the body. From the body, I moved backward in time, outside of the abandoned building. There I found the tracks of a cab and two pairs of footprints: one tall, based on length of the stride; one not so tall. Since the dead body was not so tall, I concluded that I must look for the tall one as the murderer. I knew that having some idea of the motive would help me find the killer. It wasn’t a robbery – there were still items of value on the dead body plus that gold ring in the room. But I did know from the ring we found that there was a woman involved. Since, er, John Smith did have identification on him, I asked Inspector No One Very Important to look into his background in the United States of America. Inspector No One Very Important being the sort of inspector he is, he, of course, neglected to do so. So I did it myself. That is when I learned of, er, John Smith’s marriage to Lucy Fur, and her subsequent death soon after, and further learned that, er, John Smith had taken out a protection order against one Jefferson Hope. From there it was easy to conclude that Jefferson Hope was likely the tall man as well as the driver of the cab. Once a cabbie, always a cabbie – or at least for a little while, for it would have appeared too strange for him to suddenly stop. I sent Waggins and Company to ask for Jefferson Hope at every cab service in the city, and there you have it.” He wiped one paw against the other. “Case closed.”