Sir Arthur Rusholm immediately communicated with Scotland Yard, and the utter confusion which followed this gruesome discovery had only partially subsided when I, Murray Wigan, entered the house to enquire into a mystery which was certainly amongst the most remarkable I have ever had to investigate. Some of those invited to the funeral had left the house before I arrived, but the more personal friends were still there, and the story as I have set it down was corroborated by different people with a wealth of detail which seemed to leave nothing unsaid. Besides interviewing Sir Arthur and the doctor, I saw Lady Rusholm for a few moments. She was exceedingly agitated, as was natural, and I only asked her one or two questions of a quite unimportant nature, but I was glad to see her. I like to get into personal touch with the various people connected with my cases as soon as possible. I was in the house two hours or more, questioning servants, examining doors and windows, and, to be candid, my investigations told me little. When I left Queen's Square I knew I had a complex affair to deal with, and it was natural my thoughts should fly to the one man who might help me. If I could only interest Christopher Quarles in the case! I remember speaking casually of a well-known person once and being met with the question: Who is he? It may be that some of you have never heard of Christopher Quarles, professor of philosophy, and one of the most astute crime investigators of this or any other time. It has been my privilege to chronicle some of our adventures together, and his help has been of infinite benefit to me. Without it, not only should I have failed to elucidate some of those mysteries the solving of which have made me a power in the detective force, but I should never have seen his granddaughter, Zena, who is shortly to become my wife. For some months past the professor had given me no assistance at all. He would not be interested in my cases, and would not enter the empty room in his house in Chelsea where we had had so many discussions. It was a fad of his that he could think more clearly in this room, which had only three chairs and an old writing table in it, yet perhaps I ought not to call it a fad, remembering the results of some of our consultations there. Months ago we had investigated a curious case in which jewels had been concealed in a wooden leg. The solution had brought us a considerable reward, and upon receiving the money Quarles had declared he would investigate no more crimes. He had kept his word, had locked up the empty room, and although I think I had sorely tempted him to break his vow on more than one occasion, I had never quite succeeded. As I got into a taxi I considered how very seldom it is that the ruling passion ever dies. The Queen's Square mystery ought to shake Quarles's resolution if anything could. Zena was out when I got to Chelsea, but the professor seemed pleased to see me.