It will be remembered that of all the inmates of the house, Dr. Hansen was the only one who had a personal acquaintance with Watson.  One year before the doctor had seen him a shadow—­wasted, worn, exhausted.  He had talked with him on that memorable night in the cafe.  Well he remembered the incident, and the subject of that strange conversation—­the secret of life that had been discovered by the missing Dr. Holcomb.  And Dr. Hansen had pondered it often since.

What was the force that was pulsing through the Blind Spot?  It had reached out on the earth, and had plucked up youth as well as wisdom.  This was the first time it had ever given up that which it had taken!

It was Watson, sure enough; but it was not the man he had known one year before.  Except for the basic features Hansen would not have recognized him; the shadow was gone, the pallor, the touch of death.  He was hale and radiant; his skin had the pink glow of alert fitness; except for being dazed, he appeared perfectly natural.  In the tense moment of his arrival the little group waited in silence.  What had he to tell them?

But he did not see them at first.  He groped about blindly, moving slowly and holding his hands before him.  His face was calm and settled; its lines told decision.  There was not a question in any mind present but that the man had come for a purpose.

Why could he not see?  Perhaps the light was too dim.  Some one thought to turn on the extra lights.

It brought the first word from Watson.  He threw up both arms before his face; like one shutting out the lightning.

“Don’t!” he begged.  “Don’t!  Shut off the lights; you will blind me!  Please; please!  Darken the room!”

Sir Henry sprang to the switch.  Instantly the place went to shadow; there was just enough light from the moon to distinguish the several forms grouped in the middle of the room.  Dr. Hansen proffered a chair.

“Thank you!  Ah!  Dr. Hansen!  You are here—­I had thought—­This is much better!  I can see fairly well now.  You came very near to blinding me permanently!  You didn’t know.  It’s the transition.”  Then:  “And yet—­of course!  It’s the moon!  The moon!”

He stopped.  There was a strange wistfulness in the last word.  And suddenly he rose to his feet.  He turned in gladness, as though to drink in the mellow flow of the radiance.

“The moon!  Gentlemen—­doctor—­who are these people?  This is the house of the Blind Spot!  And it is the moon—­the good old earth!  And San Francisco!”

He stopped again.  There was a bit of indecision and of wonder mixed with his gladness.  The stillness was only broken by the scarcely audible voice of Mme. Le Fabre.

“Now we know!  It is proven.  The sceptics have always asked why the spirits work only in the half light.  We know now.”

Watson looked to Dr. Hansen.  “Who is this lady?  Who are these others?”