However, his superiors appeared to be satisfied, and, towards the beginning of June Hanslet went off upon his long postponed leave. The Professor’s time was fully occupied in correcting the proofs of _Some Aspects of Modern Thought_, which were now coming in from the printer, whose reader, appalled by some of the Professor’s strictures upon his contemporaries, had scattered here and there across the margin the ominous words “Query, libellous?” To each of these the Professor added the note: “Nonsense!” in letters half an inch long at least. It was perhaps fortunate for the conscientious reader that he was beyond the reach of the Professor’s tongue. The rigid police protection which had at first been imposed upon both the Professor and Mr. Ludgrove had been gradually relaxed until now it had dwindled to nothing more serious than a casual glance at their houses by the constable on beat when he happened to pass them. The professor himself appeared to have forgotten the warning given to him by the Black Sailor, and to have acquiesced in the official view that, since the perpetrator had committed suicide, nothing further would be heard of the murders. It was while matters were in this state that Dr. Priestley received one Saturday morning a letter which obviously caused him some satisfaction. It was signed “Elmer Ludgrove” and was written in a curiously neat and clerkly hand. The contents of it were as follows: “Dear Sir. I should not venture to write to you, but for the fact that I know that you are as interested in the recent affair of the numbered counters as I am myself. I have recently come across, wholly by accident, certain curious facts which may serve to throw an entirely fresh light upon the deaths of six men, which, to my mind, have not yet been satisfactorily explained. I am not anxious to approach the police, at least until I have consulted you. The police, as is perhaps natural, could scarcely be expected to welcome disclosures which would completely upset their official theory. They believe, as I confess I did at one time myself, that the late Mr. Copperdock was guilty, and that his mania finally culminated in his own suicide. “If I am correct in my deductions from the new evidence which has come into my hands, I can prove beyond question that Mr. Copperdock was innocent, indeed, that he himself fell a victim to the agency which committed the other murders. I must ask you to respect my confidence until you have allowed me to put my evidence before you. When this has been done, I shall ask your advice as to the best means of laying it before the authorities. You, I have reason to believe, are on friendly terms with Inspector Hanslet, and perhaps you will agree, when you have examined the evidence I shall put before you, that it will be best to call him into consultation.