“Half a minute,” I said eagerly, “let’s have a look. The knife is in position for sharpening a pencil and the back of the knife is pointing to my chest. The marks are underneath.” I took a pencil from my pocket and tried it. “Yes, I’ve got you, Dennis. It’s quite clear. If I held the knife with the point to my right instead of to my left, as I should do in sharpening with my left hand, the marks appear on the other side of the blade. It is not quite conclusive, Den, but it’s jolly cute.”
“Not when you’re looking for it,” he said. “I was struck by the fact that the knife which, by its size and weight, was a seaman’s handy tool, had also been used for the repeated sharpening of a blue pencil. When I saw those indications I went through the motion and came to the conclusion that the marks were on the wrong side. Then I tried with my left hand and accounted for it. The blue pencil made me suspicious. I have no knowledge of a yacht-hand’s duties, but surely sharpening blue pencils is not one of them. Then the knife had also been carried in the same pocket as a piece of white chalk. The only sort of person I could think of who would carry a piece of chalk loose in his pocket and use a blue pencil continuously was a schoolmaster. So I stated definitely—there’s nothing like bluff—that the knife belonged to the left-handed man, who quite obviously had red hair, who appeared to wear the insignia of the married state, and who—again according to the law of averages—had at least one child. I naturally slumped the schoolmaster idea in with it, and there you have the whole thing in a nutshell. But it was Garnesk who set me looking for left-handed clues, and if I hadn’t been looking for it, it would never have entered my head.”
“But look here,” I suggested, “some people sharpen pencils by pointing the pencil to them. Wouldn’t that produce the same effect?”
“Yes,” he admitted, “I thought of that. But the marks would have been very much fainter, because there would have been much less pressure. I put that idea aside.”
“Good!” I exclaimed. “I should much prefer to swallow your theory whole, Dennis, but it struck me that might be a possible source of error, which, of course, might have led us on to a false trail. And, I say, those questions you asked about the time he stayed in port and the hotel. Were those all bluff? Or had you some sort of idea at the back of them?”
“I had a very definite idea at the back of them,” Dennis replied. “I thought perhaps the white chalk which was deposited in the blade-pocket, and was even noticeable on the handle, might be due to billiard chalk. But, of course, I didn’t mention billiards, because it would have given my line of reasoning away. I thought it was better to spring it on them with a bump.”
“Which you certainly did,” I laughed. “As a matter of fact, I thought you were simply having a game with us all. But now that you’ve told me the details, Den, do you remember what happened when you did spring it on them?”
“Well, of course I do,” he replied. “But even so, I hardly know what to make of it. I should like to feel confidently that Fuller is the man we are after. But we must remember that both he and Hilderman might very easily have thought I really had discovered something from the knife and been exceedingly surprised without having any guilty connection with the discovery.”
“H’m,” I muttered, “I prefer to suspect Fuller.”