For a moment I stood, trying to conceal the chill coursing through my veins, puzzling what to do next. I decided to search the house thoroughly. If I found no sign of the professor or his guest, I would call in the police. Fearfully yet willingly the aged couple led me from room to room, from attic to basement, until but one place remained--the laboratory. I hesitated for several seconds at the closed door of my friend's workroom. Not that I had never entered the--to a layman's eyes--weirdly-appointed place. I had been in many times with the professor. But this time I dreaded what I might find. * * * * * Pulling myself together, I gently tried the door. To my horror it yielded to my touch. Alive, the professor always kept it locked. A new dread assailed me, as, flinging the door wide open, I blinked in the sudden glare of powerful globes. Someone had left the lights full on! Horrified I stood and stared, knowing by their heavy breathing that the aged couple were also staring with fright-widened eyes. Afraid of what? I did not know. I only knew that the atmosphere had become even more sinister. I knew that something dreadful had taken place in that room. Trembling with consternation I forced myself to take a few steps forward, then I again stared about me. At one end of the large room something shone brightly in the glow of the lights. Slowly I walked across to examine it: it appeared to be a glass case, almost like a show-case, about eight feet square and seven feet in height. With the mechanical actions of the mentally distraught I walked all around it. Not the slightest sign of an entrance could I see. The fact intrigued me. I tapped lightly on the highly polished surface with my fingers. It rang to my touch like cut glass. Through the transparent surface I could see John and his wife. They were watching me furtively, wondering, no doubt, why I lingered. As I looked at them John suddenly lumbered up to the case on the opposite side. Dropping to his knees, he stared. Turning an imploring gaze to me, he pointed. His lips moved soundlessly. I followed the pointing finger with my eyes; gasped at what I saw. Near the center of the cage, on the floor constructed of the same crystalline substance, something glittered, its brilliance almost dazzling as the light rays struck it. My face pressed close to the cold outer surface of the structure, my shocked intelligence gradually realized what that small sparkling object was. It was a magnificent diamond--and the professor had always worn a diamond ring! * * * * * In a sudden frenzy of horror I pawed my way around the cage to where John still knelt. As I reached him he jerked his head in a numb way as he croaked, "It's a diamond, sir! The professor's!"