“Having got so far, my next step was, of course, to examine into the details of the crime, and to see how far they would help us. I went up to the house with the Inspector, and saw all that was to be seen. The wound upon the dead man was, as I was able to determine with absolute confidence, fired from a revolver at the distance of something over four yards. There was no powder-blackening on the clothes. Evidently, therefore, Alec Cunningham had lied when he said that the two men were struggling when the shot was fired. Again, both father and son agreed as to the place where the man escaped into the road. At that point, however, as it happens, there is a broadish ditch, moist at the bottom. As there were no indications of bootmarks about this ditch, I was absolutely sure not only that the Cunninghams had again lied, but that there had never been any unknown man upon the scene at all.
“And now I have to consider the motive of this singular crime. To get at this, I endeavoured first of all to solve the reason of the original burglary at Mr. Acton’s. I understood, from something which the Colonel told us, that a lawsuit had been going on between you, Mr. Acton, and the Cunninghams. Of course, it instantly occurred to me that they had broken into your library with the intention of getting at some document which might be of importance in the case.”