It was not until the colour had come back and the blue had regained its lustre that either of us looked up. Could such a thing be unravelled? Fenton turned the stone over thoughtfully. He shook his head. “In that jewel, Harry, lies the secret. I wish I knew a bit more about physics, light, force, energy, vibration. We have got to know.” “Your theory?” “It still holds good.” I thought. “Let me get it clear, Hobart. You say that we catch only certain vibrations.” “That's it. Our eyes are instruments, nothing else. We can see light, but we cannot hear it. We hear sound, but we cannot see it. Of course they are not exactly parallel. But it serves the point. Let's go a bit further. The eye picks up certain vibrations. Light is nothing but energy vibrating at a tremendous speed. It has to be just so high for the eye to pick it up. A great deal we do not get. For instance, we can only catch one-twelfth of the solar spectrum. Until recently we have believed only what we could see. Science has pulled us out of the rut. It may pull us through the Blind Spot.” “And beyond.” Hobart held up his hands. “It is almost too much to believe. We have made a discovery. We must watch our step. We must not lose. The work of Dr. Holcomb shall not go for nothing.” “And the ring?” He consulted his watch. “We have only a short time left. We must map our action. We have three things to work on--the ring, the house, Bertha Holcomb. It's all up to you, Harry. Find out all that is possible; but go slow. Trace down that ring; find out everything that you can. Go and see Bertha Holcomb. Perhaps she can give you some data. Watson said no; but perhaps you may uncover it. Take the ring to a lapidary; but don't let him cut it. Last of all, and most important, buy the house of the Blind Spot. Draw on me. Let me pay half, anyway.” “I shall move into it,” I answered. He hesitated a bit. “I am afraid of that,” he answered. “Well, if you wish. Only be careful. Remember I shall return just as soon as I can get loose. If you feel yourself slipping or anything happens, send me a cable.” The hours passed all too quickly. When day came we had our breakfast and hurried down to the pier. It was hard to have him go. His last words were like Hobart Fenton. He repeated the warning. “Watch your step, Harry; watch your step. Take things easy; be cautious. Get the house. Trace down the ring. Be sure of yourself. Keep me informed. If you need me, cable. I'll come if I have to swim.” His last words; and not a year ago. It seems now like a lifetime. As I stood upon the pier and watched the ship slipping into the water, I felt it coming upon me. It had grown steadily, a gloom and oppression not to be thwarted; it is silent and subtle and past defining--like shadow. The grey, heavy heave of the water; the great hull of the steamer backing into the bay; the gloom of the fog bank. A few uncertain lines, the shrill of the siren, the mist settling; I was alone. It was isolation.