They walked down Praed Street without adventure, and Mr. Ludgrove unlocked the door of his shop with his latchkey. They passed through it into the inner room, the window of which was already curtained and the gas lighted. Dr. Priestley cast a swift glance round it, noting with interest the scientific instruments on the bench, the cases full of books, and two comfortable armchairs. “This is a very comfortable room of yours, Mr. Ludgrove,” he remarked approvingly. “It has heard some queer stories in its time,” replied Mr. Ludgrove with a smile. “You can form no idea of the extraordinary confessions which some of my clients force me to listen to. But I can assure you that it has heard nothing more amazing that the story which I am about to unfold to you this evening.” “May I ask a question before you begin, Mr. Ludgrove?” said the Professor quietly. “Certainly, pray ask as many as you please,” replied Mr. Ludgrove with a smile. “How did you learn of my interest in this affair? So far as I am aware, it is not common property.” “I am afraid that Inspector Hanslet was indiscreet,” replied Mr. Ludgrove. “When he first took over the case, he came here and had a long talk with me. He said then that he would put the facts before one whose powers of deduction were unrivalled. When I next saw him, he happened to mention your name, which I already knew as that of the boldest and most enterprising scientist of the age. It required very little intelligence on my part to infer that you would be interested in these extraordinary happenings, and that you were scarcely likely to accept the official explanation of them.” “I see,” said the Professor. “Well, as it happens, your inference is correct. I am greatly interested, and I have a theory of my own as to the motive for the murders, which the police have been pleased to reject. I am all the more anxious to hear the evidence you have to put before me. There is still one more point in which I am interested. I am informed that, sometime before his death, Mr. Copperdock reported that he had met an individual known as the Black Sailor. Upon this being reported to you, you stated that you happened to have Mr. Copperdock under observation at the moment when he stated the meeting took place, and that no Black Sailor was present. Is this correct?” “I can assure you, Dr. Priestley, that at that moment there was nobody in sight but Mr. Copperdock and myself,” replied Mr. Ludgrove simply. “Thank you,” said the Professor. “Now, I am prepared to examine the evidence you have to show me.” Mr. Ludgrove rose from his chair. “Will you excuse me for a few minutes, Dr. Priestley?” he said. “Before I begin my explanation, I should like to fetch certain things which I have put in a place of security upstairs. I will not keep you very long.”