"The Blue Disease is spreading in London," he remarked shortly, and returned to his paper. I felt rebuffed, but reflected that this, after all, was how an average man might be expected to behave. "A curious business," I continued. "I am a doctor, and therefore very much interested in it." His manner changed. He assumed the attitude of the average man towards a doctor at once, and I was gratified to observe it. "I was just thinking I'd like to hear what a doctor thinks about it," he said, laying down his paper. "I thought of calling in on Dr. Sykes on my way home to-night; he attends my wife. Do you know Dr. Sykes?" "Which one?" I asked cautiously, not willing to disappoint him. "Dr. Sykes of Harlesden," he said, with a look of surprise. "Oh, yes, I know Dr. Sykes. Why did you think of going to see him?" He smiled apologetically and pointed to the paper. "It sounds so queer ... the disease. They say, up in Birmingham, that it's stopping all diseases in the hospitals ... everywhere. People getting well all of a sudden. Now I don't believe that." "Have you seen a case yet?" "Yes. A woman. In the street this afternoon as I was coming from lunch. The police took her. She was mad, I can tell you. There was a big crowd. She screamed. I think she was drunk." He paused, and glanced at me. "What do you think of it?" I took a deep breath. "I don't _think_, I _know_," I said, in as quiet a manner as possible. He stared a moment, and a nervous smile appeared and swiftly vanished. He seemed uncertain what to do. "You've found out something?" he asked at length, playing with his teaspoon and keeping his eyes on the table. I regarded him carefully. I was not quite certain if he still thought I was a doctor. "I'm not a lunatic," I said. "I'm merely stating a rather extraordinary fact. I know all about the germ of the Blue Disease." He raised his eyes for an instant, and then lowered them. His hand had stopped trifling with the teaspoon. "Yes," he said, "the doctors think it's due to a germ of some sort." He made a sort of effort and continued. "It is funny, some of these germs being invisible through microscopes. Measles and chickenpox and common things like that. They've never seen the germs that cause them, that's what the papers say. It seems odd--having something you can't see." He turned his head, and looked for his hat that hung on a peg behind him. "One moment," I said. I took out my card-case. "I want you to read this card. Don't think I'm mad. I want to talk to you for a particular reason which I'll explain in a moment." He took the card hesitatingly and read it. Then he looked at me. "The reason why I am speaking to you is this," I said. "I want to find out what a decent citizen like yourself will think of something I know. It concerns the Blue Disease and its origin." He seemed disturbed, and took out his watch. "I ought to get home. My wife----" "Is your wife ill?" "Yes." "What's the matter with her?" He frowned.