"Good-bye, Doctor Colkirk," Beryl said, looking into my eyes as I held her small hand. "I hope we shall soon meet down in Wiltshire, and, when we do, let us forget all the mystery of yesterday." "I suppose you have given Hoefer permission to visit, the room when he wishes to pursue his investigations?" I said, turning to her ladyship. "Of course. The house is entirely at his disposal. One does not care to have a death-trap in one's own house." "He will do his best--of that I feel quite sure," I said. And then again promising to visit her soon, I shook her hand, bade them both adieu, and with a last look at the frail, graceful woman I loved, went out into the hot, dusty street. In order to celebrate my sudden accession to wealth I lunched well at Simpson's, and then took a hansom to old Hoefer's dismal rooms in. Bloomsbury. To me, so gloomy and severe is that once-aristocratic district that, in my hospital days, I called it Gloomsbury. Hoefer occupied a dingy flat in Museum Mansions, and, as I entered the small room which served him as laboratory, I was almost knocked back by the choking fumes of some acid with which he was experimenting. A dense blue smoke hung over everything, and through it loomed the German's great fleshy face and gold-rimmed spectacles. He was in his shirt-sleeves, seated at a table, watching some liquid boiling in a big glass retort. Around his mouth and nose a damp towel was tied, and as I entered he motioned me back. "Ach! don't come in here, my tear Colkirk! I vill come to you. Ze air is not good just now. Wait for me there in my room." Heedless of his warning, however, I went forward to the table, coughing and choking the while. I took out my handkerchief, when suddenly he snatched it from me, and steeped it in some pale yellow solution. Then, when I placed it before my mouth, inhaling it, I experienced no further difficulty in respiration. The nature of the experiment on which he was engaged I could not determine. From the retort he was condensing those suffocating fumes, drop by drop, now and then dipping pieces of white, prepared paper into the liquid thus obtained. I stood by watching in silence. Once he placed a drop of that liquid upon a glass slide, dried it for crystallisation, and, placing it beneath the microscope, examined it carefully. He grunted. And I knew he was not satisfied. Then he added a few drops of some colourless liquid to that in the retort, and the solution at once assumed a pale green hue. He boiled it again for three minutes by his common, metal watch, then, having drained it off into a shallow glass bowl to cool, blew out his lamp, and I followed him back into his small, cosy, but rather stuffy little den. "Well?" he inquired. "You have called at her ladyship's--eh?" "Yes," I replied, stretching myself in one of his rickety chairs; "but you were there before me. What have you discovered?" "Nothing."