As time passed he grew more daring and more truculent, and it is believed he was the author of the well-known murder of Begbie, the porter of the British Linen Company Bank--a crime never brought home to him, however, the murder remaining a mystery to the last. This victim, returning from Leith carrying a large parcel of bank-notes, was stabbed in the back at the entrance of Tweeddale's Court. Several persons were suspected, apprehended, and discharged for want of evidence. Yet the most active measures were taken to detect the crime. "Hue-and-cry" bills were thrown off during the night, and despatched next morning by the mail-coaches to all parts of the country. It was stated in this notice that "the murder was committed with a force and dexterity more resembling that of a foreign assassin than an inhabitant of this country. The blow was directly to the heart, and the unfortunate man bled to death in a few minutes." Through Mr. Denovan's investigations many facts were obtained to implicate Mackoull, but the proof of his guilt was still insufficient. One of the most suspicious facts against him was that later on he was often seen in the Belle Vue grounds, and here, in an old wall, many of the notes stolen from the murdered porter were presently discovered. They were those of large value, which the perpetrator of the crime would find it difficult to pass. Reports that they had been thus found, and in this particular wall, were in circulation some three weeks before they were actually unearthed, and it is believed the story was purposely put about to lead to their recovery. It is a curious fact that the stonemason who came upon the notes in pulling down the wall resided close to the spot where the murder had been committed. But for the good luck that he was able to prove clearly that he was not in Edinburgh at the time of the murder, he might have been added to the sufficiently long list of victims of circumstantial evidence.