“I suggest, as the various exhibits to which I shall be compelled to refer are at present at my house, and as it may be necessary for me to point out to you certain peculiarities of the locations in which the murders took place, that your examination be carried out there. As I believe that as little time as possible should be wasted, I suggest, if it meets with your approval, that you should do me the honour of calling upon me this evening. As, in the light of recent events, you may not care to come to Praed Street alone, I propose to call upon you after your dinner this evening, and to learn your wishes in the matter. If you agree to my suggestion, we can then walk to my house together. I am, sir, yours faithfully, “Elmer Ludgrove” The Professor read this letter through twice. His final conclusion was that this man Ludgrove had in some way discovered that the dead men had all been members of the Morlandson jury. After all, he knew from the Black Sailor’s words that Ludgrove had made inconvenient enquiries, and it was possible that he had somehow stumbled upon the truth. Anyway, there could be no harm in going to see him and hearing what he had to say. Besides, he had never conveyed to him the Black Sailor’s warning. Hanslet might have, but the Professor, who had penetrated the ill-concealed scepticism of the Inspector, considered this unlikely. In any case, by comparing notes with this man, who had been living in Praed Street throughout the period of the murders, he might derive a hint which would lead him to his goal. For Dr. Priestley, although he appeared to have put the whole affair out of his mind, was in fact determined to find the solution of the problem. He felt that so far the part he had played had been a distinctly ignominious one. Both his theory of the motive of the crimes and his account of his meeting with the Black Sailor had been disregarded. And although Dr. Priestley affected to regard his excursions into the solution of criminal problems with half-amused tolerance, his ill-success hitherto in this instance was a secret, but none the less bitter, blow to his pride. Yes, he would certainly go to see this man Ludgrove. His letter showed him to be a man above the ordinary standard of education of people in his position. Hanslet had spoken of him as a man of considerable intelligence. The Professor, considering the matter, felt that he might well have got into touch with him before. He began to think that he had been too ready to rely upon the police descriptions of the events which had taken place, and had neglected an alternative source of information which might contain many details of value. And, his determination made, the Professor fidgeted all day until, having hurried through dinner and found himself in his study earlier than usual, he could expect his visitor.