“I was at first puzzled to think of any such mark. And then, during a visit to Mr. Copperdock, the idea came to me. I saw a box full of white bone counters lying on his table, and I managed to appropriate a dozen or so of these. At the same time I carefully noted the envelopes he used in his business, and by a casual question learnt where he had obtained them. I bought three thousand of these, all the remaining stock, giving the name of Mr. Copperdock. There was very little chance of their being traced, but if they had been, the result of inquiries would have shown that they had all been sold to the tobacconist.
“I also discovered that the typewriter recently purchased by Mr. Copperdock was a Planet, and I took a careful note of the brand of pen and red ink he habitually used. I next made enquiries among the envelope addressing agencies, until I found one which employed Planet machines. To this agency I sent my envelopes, together with a telephone directory in which I had marked some two thousand names, among which were those of my intended victims who happened to have a telephone. To this list I added one of my own, containing a thousand additional names, among them the jurymen I had not found in the telephone book. I instructed the agency to type these names and addresses on the envelopes. It was a safe assumption that a year later, when I began operations, the agency would not remember having typed the names of the dead men among so many thousands of others. The counters I numbered myself, as required.
“Last November, I felt myself in a position to seek my first victim. I decided that it should be Mr. Tovey, a personal friend of Mr. Copperdock, from whom I had learnt all I required to know about his habits. I had, among my other weapons, a paper cutter’s knife, with half a dozen blades. These blades I had sharpened along both edges until they resembled daggers, and I had discovered a means of fixing them lightly into the handle, so that they would remain in the wound, leaving me free to carry off the handle.
“That evening, Mr. Ludgrove took his usual walk, returning by way of Paddington station. From here he telephoned to Mr. Tovey, giving him the message that he was wanted at St. Martha’s. Mr. Ludgrove then walked back here, and took on the character of the Black Sailor. Behind this shop is a piece of ground which was once a garden, and that in turn is separated by a low wall from a yard, deserted after business hours, with gates and also a small door leading into a back street. I had made myself a key to the small door, and it provided me with an alternative means of access to this house.
“The Black Sailor went out this way, waited in the shadows at the corner of the back street until he saw Mr. Tovey pass, then followed him and caught him up among the crowd outside the Express Train. The knife required no violence in its use, merely a firm push in one of the spots which Dr. Morlandson had shown me. The actual stabbing was a very simple matter, and the Black Sailor disappeared in the crowd, to return here by the way he went out and transform himself into Mr. Ludgrove.
“But I realized that this method, although it had served its purpose once, was inartistic and dangerous. There was always the risk that the Black Sailor might be recognized and traced back here. As a matter of fact, Wal Snyder had noticed him, but his evidence was discredited. The police, however, were compelled to offer a reward for him, and I determined that the Black Sailor must be reserved for special purposes.
“In the case of Mr. Colburn I adopted quite a different method. I had become a customer of his, and had encouraged his son to confide in me. From him I gradually learnt his father’s habits and peculiarities, particularly that of smoking a pipe in the shop after lunch, and, when he had finished it, of refilling it and putting it away on a shelf. I examined the pipe in young Colburn’s absence, and noticed that it was cracked. That evening, I visited a tobacconist at some distance from here and bought a pipe of similar make and shape.
“Within a few days, as I had expected, I saw Mr. Colburn enter Copperdock’s shop. It was a fair assumption that he had gone in to buy a new pipe to replace the old one, since I had learnt that his tobacco was always delivered to him. I took a very small splinter of glass, covered it with a preparation which Dr. Morlandson had given me, and drove one end of it into a notch I had made in the mouthpiece of the pipe I had bought. I then went to Colburn’s shop, on an errand which necessitated young Colburn’s going to the bakehouse and leaving me alone. I saw, as I had expected, a new pipe lying filled on the shelf. I substituted mine for it, put Mr. Colburn’s pipe in my pocket, waited until young Colburn came back with my purchase, and left the shop. I was in the country when Mr. Colburn died, but I heard the details later, as no doubt you have heard them, Dr. Priestley.”
“Yes, the deaths of Colburn and Martin strengthened my theory that Dr. Morlandson was at the bottom of the affair,” replied the Professor calmly. “I guessed that there was extensive medical knowledge behind both of them.” His one idea was to
