"Two days later this same performance was gone through under exactly similar circumstances. Again I changed my dress, again I sat in the window, and again I laughed very heartily at the funny stories of which my employer had an immense repertoire, and which he told inimitably. Then he handed me a yellow-backed novel, and moving my chair a little sideways, that my own shadow might not fall upon the page, he begged me to read aloud to him. I read for about ten minutes, beginning in the heart of a chapter, and then suddenly, in the middle of a sentence, he ordered me to cease and to change my dress.
     "You can easily imagine, Mr. Holmes, how curious I became as to what the meaning of this extraordinary performance could possibly be. They were always very careful, I observed, to turn my face away from the window, so that I became consumed with the desire to see what was going on behind my back. At first it seemed to be impossible, but I soon devised a means. My hand-mirror had been broken, so a happy thought seized me, and I concealed a piece of the............