“He never knew of one.  It was none of his business.  He was merely a labourer, and did what he was paid for.”

“Do you know who built it?”

“Some old guy.  He was a cranky cuss with side-whiskers.  He used to wear a stove-pipe hat.  I think he was a chemist.  Whenever he showed up he would run us kids out of the building.  I think he was a bachelor.”

This was all the information he could give, but it was a great deal.  Certainly it was more than I had hoped for.  The house had been built by a chemist; even in the construction there was mystery.  I had never thought of a second cellar; when I had explored the building I had taken the stone wall for granted.  It was so with Jerome.  It was the first definite clue that really brought us down to earth.  What had this chemist to do with the phenomena?

After all, behind everything was lurking the mind of man.

We hastened back to the house and into the cellar.  By merely sounding along the wall we discovered the door; it was cleverly constructed and for a time defied our efforts; but Jerome got it open by means of a jemmy and a pick.  The outside was a clever piece of sham work shaped like stone and smeared over with cement.  In the dim light we had missed it.

We had high expectations.  But we were disappointed.  The space contained nothing; it was smeared with cobwebs and hairy mould; but outside of a few empty bottles and the gloomy darkness there was nothing.  We tapped the walls and floor and ceiling.  Beyond all doubt the place once held a secret; if it held it still, it was cleverly hidden.  After an hour or two of search we returned to the upper part of the building.

Jerome was not discouraged.

“We’re on the right track, Mr. Wendel; if we can only get started.  I have an idea.  The chemist—­it was in ’ninety-one—­that’s more than twenty years.”

“What is your idea?”

“The Rhamda.  What is the first thing that strikes you?  His age.  With everyone that sees him it’s the same.  At first you take him for an old man; if you study him long enough, you are positive that he is in his twenties.  May he not be this chemist?”

“What becomes of the doctor and his Blind Spot?”

“The Blind Spot,” answered Jerome, “is merely a part of the chemistry.”

Next day I hunted up a jeweller.  I was careful to choose one with whom I was acquainted.  I asked for a private consultation.  When we were alone I took the ring from my finger.

“Just an opinion,” I asked.  “You know gems.  Can you tell me anything about this one?”

He picked it up casually, and turned it over; his mouth puckered.  For a minute he studied.

“That?  Well, now.”  He held it up.  “Humph.  Wait a minute.”

“Is it a gem?”

“I think it is.  At first I thought I knew it right off; but now—­ wait a minute.”

He reached in the drawer for his glass.  He held the stone up for some minutes.  His face was a study; queer little wrinkles twisting from the corners of his eyes told his wonder.  He did not speak; merely turned the stone round and round.  At last he removed his glass and held up the ring.  He was quizzical.