“There is no telling what may happen,” he said.  “For my own part I shall not venture near the Spot of Life until just at the end.  I shall remain in the chamber underneath.

“But you two ought to show yourselves immediately after sundown.  Certain ancient writings indicate it.  You, and the Nervina, will have to mount the stair to the Spot, and remain in sight until midnight—­until the end.

“So we must be prepared for accidents.”  He took some papers from his pocket, and selected two, and gave one to each of his pupils.  “Here are the details of what must be done.  In case only one of us gets through, it will be enough.”

“But—­how can these be of any use, on such short notice?” Harry asked.

“Cudgel your brains a bit, gentlemen,” he chided good-humouredly.  “You will soon see my drift.  This is one of those occasions when the psychic elements involved are such that, without doubt, it were best if you reacted naturally to whatever may happen.

“Now you will note that I have made a drawing of the Blind Spot region; also certain calculations which will explain themselves.

“Moreover, I have written out the combination to my laboratory safe in my house in Berkeley.  The green stone is there.  Bertha will help, as soon as she understands that it is my wish; no explanation will be needed.

“You may leave the rest to me, young gentlemen.  Act as through you had no notion that I was down below the Spot.  I shall be merely experimenting a bit with that circle of jewels, to see if the phenomena which affected the Aradna cannot be repeated.  I fancy it was not mere accident, but rather the working of a ‘period.’”

He said no more about this, except to comment that he hoped to get into direct communication with Hobart Fenton before midnight should arrive.  However, he did say, in an irrelevant sort of manner: 

“Oh, by the way—­do either of you happen to recall which direction the house at Chatterton Place faces?”

“North,” replied Harry and Chick, almost in the same breath.

“Ah yes.  Well, the temple faces south.  Can you remember that?”

They thought they could.  The rest of the meal was eaten without any discussion.  Just as they arose, however, the doctor observed: 

“It may be that Hobart Fenton has got to come through.  I wish I knew more about his mentality; it’s largely a question of psychic influence—­the combined, resultant force of the three material gems, and the three degrees of psychic vibration as put forth by him and you two.  We shall see.

“Something happened today—­the Geos told me about it—­which may link up Hobart very definitely.  It was about one o’clock when one of the temple pheasants began to behave very queerly up on the great stair.  It had been walking around on the snow-stone, and flying a bit; then it started to hop down the steps.

“About sixteen steps down, Geos says the pheasant stopped and began to flutter frantically, as though some unseen person were holding it.  Suddenly it vanished, and as suddenly reappeared again.  It flew off, unharmed.  I can’t quite account for it, but—­ well, we’ll see!”