When I reached London it was dusk, and a light mist hung in the darkening air. The lamps were twinkling in the streets. I decided to get some tea in a restaurant adjoining the station. When I entered it was crowded, and the only seat that was empty was at a small table already occupied by another man. I sat down, and gave my order to the waitress, and remained staring moodily at the soiled marble surface of the table. My neighbour was engrossed in his paper.

During my journey from Cambridge I had come to a certain conclusion. Sarakoff was of the opinion that we should publish a statement about the germ of immortality, and now I was in agreement with him. For I had been reflecting upon the capacity of human mind for retaining secrets and had come to the conclusion that it is so constructed that its power of retention is remarkably small. I felt that it would be a matter of extraordinary relief if everyone in that tea-shop knew the secret of the Blue Germ.

I began to study the man who sat opposite me. He was a quietly dressed middle-aged man. The expression on his rather pale, clean-shaven face suggested that he was a clerk or secretary. He looked reliable, unimaginative, careful and methodical. He was reading his newspaper with close attention. A cup of tea and the remains of a toasted muffin were at his elbow. It struck me that here was a very average type of man, and an immense desire seized upon me to find out what opinion he would pronounce if I were to tell him my secret. I waited until he looked up.

"Is there any news?" I asked.

He observed me for a moment as if he resented my question.

"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.

"Dr. Sykes thinks it's lung trouble."

"Consumption?"

He nodded, and an expression of anxiety came over his face."Good," I exclaimed. "Now listen to what I have to say. Before the week is out your wife will be cured. I swear it."

He said nothing. It was plain that he was still suspicious.

"You read what they say in the papers about the Blue Disease cutting short other diseases? Well, that Blue Disease will be all over London in a day or two. Now do you understand?"

I saw that I had interested him. He settled himself on his chair, and began to examine me. His gaze travelled over my face and clothes, pausing at my cuff-links and my tie and collar. Then he looked at my card again. Inwardly he came to a decision.

"I'm willing to listen to what you've got to say," he remarked, "if you think it's worth saying."

"Thank you. I think it's worth hearing." I leaned my arms on the table in front of me. "This Blue Disease is not an accidental thing. It was deliberately planned, by two scientists. I was one of those scientists."

"You can't plan a disease," he remarked, after a considerable silence."You're wrong. We found a way of creating new germs. We worked at the idea of creating a particular kind of germ that would kill all other germs ... and we were successful. Then we let loose the germ on the world."

"How?"

"We infected the water supply of Birmingham at its origin in Wales."

I watched his expression intently.

"You mean that you did this secretly, without knowing what the result would be?" he asked at last.

"We foresaw the result to a certain extent."

He thought for some time.

"But you had no right to infect a water supply. That's criminal, surely?"

"It's criminal if the infection is dangerous to people. If you put cholera in a reservoir, of course it's criminal."

"But this germ...?"

"This germ does not kill people. It kills the germs in people."

"What's the difference?"

"All the difference in the world! It's like this.... By the way, what is your name?"

"Clutterbuck." The word escaped his lips by accident. He looked annoyed. I smiled reassuringly.

"It's like this, Mr. Clutterbuck. If you kill all the germs in a person's body, that person doesn't die. He lives ... indefinitely. Now do you see?"

"No, I don't see," said Clutterbuck with great frankness. "I don't understand what you're driving at. You tell me that you're a doctor and you give me a card bearing a well-known specialist's name. Then you say you created a germ and put it in the Birmingham water supply and that the result is the Blue Disease. This germ, you say, doesn't kill people, but does something else which I don't follow. Now I was taught that germs are dangerous things, and it seems to me that if your story is true—which I don't believe—you are guilty of a criminal act." He pushed back his chair and reached for his hat. There was a flush on his face.

"Then you don't believe my tale?"

"No, I'm sorry, but I don't."

"Well, Mr. Clutterbuck, will you believe it when you see your wife restored to health in a few days' time?"He paused and stared at me.

"What you say is impossible," he said slowly. "If you were a doctor you'd know that as well as I do."

"But the reports in the paper?"

"Oh, that's journalistic rubbish."

He picked up his umbrella and beckoned to the waitress. I made a last attempt.

"If I take you to my house will you believe me then?"

"Look here," he said in an angry tone, "I've had enough of this. I can't waste my time. I'm sure of one thing and that is that you're no doctor. You've got somebody's card-case. You don't look like a doctor and you don't speak like one. I should advise you to be careful."

He moved away from the table. Some neighbouring people stared at me for a moment and then went on eating. Mr. Clutterbuck paid at the desk and left the establishment. I had received the verdict of the average man.