would need first to study the factors that bring about old age."

"Where did the Blue Disease come from? Tell me. I can surely understand
that!"

"You have read the paper, haven't you?"

"I've read that no one understands what it is, and that the doctors are
puzzled."

"How should I know where it comes from?"

She regarded me searchingly.

"You know something about it," she said positively. "Richard, you are
keeping it back from me. I have a right to know what it is."

I was silent.

"If you don't tell me, how can I trust you again?" she asked. "Don't you
see that there will always be a shadow between us?"

It was not difficult for me to guess that my guilty manner had roused
her suspicions. She had seen my agitation, and had found it
unaccountable. I resolved to entrust her with the secret of the germ.

"Do you remember that I once told you my friend, Professor Sarakoff, had
succeeded in keeping butterflies alive for over a year?"

She nodded.

"He and I have been experimenting on those lines and he has found a germ
that has the property of keeping human beings alive in the same way. The
germ has escaped ... into the world ... and it is the cause of the Blue
Disease."

"How did it escape?"

I winced. In her voice I was conscious of a terrible accusation.

"By accident," I stammered.

She jumped to her feet.

"I don't believe it! That is a lie!"

"Alice, you must calm yourself! I am trying to tell you exactly what
happened."

"Was it by accident?"

The vision of that secret expedition to the water supply of Birmingham
passed before me. I felt like a criminal. I could not raise my eyes; my
cheeks were burning. In the silence that followed, the sound of Mr.
Annot's voice became audible. Alice stood before me, rigid and
implacable.

"It was--by accident," I said. I tried to look at her, and failed. She
remained motionless for about a minute. Then she turned and left the
room. I heard her go slowly upstairs. A door banged. Actuated by a
sudden desire, I stepped into the hall, seized my coat and hat and
opened the front door. I was just in time. As I gently closed the door I
heard Mr. Annot on the landing above. He was singing some long-forgotten
tune in a strange cracked voice.

I stood outside on the doorstep, listening, until, overcome by
curiosity, I bent down and lifted the flap of the letter-box. The
interior of the hall was plainly visible. Mr. Annot had ceased singing
and was now stand