When I arrived at the Society's rooms on the evening for which I had an invitation, I found them pleasantly lighted. The various scientific diagrams and instruments had been removed, and comfortable arm-chairs were arranged so that a free passage was available, not merely to each row, but to each chair. The place was full when I entered, and soon afterwards the door was closed and locked. Natalie Brande and Edith Metford were seated beside each other. An empty chair was on Miss Metford's right. She saw me standing at the door and nodded toward the empty seat which she had reserved for me. When I reached it she made a movement as if to forestall me and leave me the middle chair. I deprecated this by a look which was intentionally so severe that she described it later as a malignant scowl. I could not at the moment seat myself voluntarily beside Natalie Brande with the exact and final knowledge which I had learnt at Scotland Yard only one week old. I could not do it just then, although I did not mean to draw back from what I had undertaken--to stand by her, innocent or guilty. But I must have time to become accustomed to the sensation which followed this knowledge. Miss Metford's fugitive attempts at conversation pending the commencement of the lecture were disagreeable to me. There was a little stir on the platform. The chairman, in a few words, announced Herbert Brande. "This is the first public lecture," he said, "which has been given since the formation of the Society, and in consequence of the fact that a number of people not scientifically educated are present, the lecturer will avoid the more esoteric phases of his subject, which would otherwise present themselves in his treatment of it, and confine himself to the commonplaces of scientific insight. The title of the lecture is identical with that of our Society--_Cui Bono?_"