"Now then," he said, as he lighted his pipe and made himself comfortable, "we'll go into the latest development. You remember what made me rush off and leave you there?"

"I remember saying something about the sunlight, and you suddenly dashed off."

"To tell you the truth, I had very little faith in the theory that at this hour, above all, the spook of the Chemist's Rock was active, until you pointed out that only about that time is the whole of the river course up to the rock, and the whole of the rock itself, flooded with sunlight. Then, when you made that remark, I suddenly felt that I ought to be on the cliff on the look out for this unknown yacht. We connect the two together in some way which we don't yet understand, so I meant to go and have a look for the ship. I saw nothing of any importance until I shouted to you. Just then I was looking through the gla.s.ses at the sh.o.r.e. I turned them on the landing-stage and along the beach, and I had just lighted on the bay where we explored this morning when suddenly, for half a second or so, all the shadows of the rocks turned a vivid green, and then as suddenly resumed their natural colour again."

"Good heavens!" I exclaimed. "Green again! Can you make anything of it at all, Garnesk? I'm sorry I'm such a duffer as to faint at the critical moment, when I might have been of some a.s.sistance to you.

What in G.o.d's name can it all mean?"

"I'm no further on," he replied bitterly; "in fact, I'm further back."

"Further back!" I cried. "How? I don't see how you can be."

"I'll tell you what my theory was about all this affair, and it struck me as a good one--strange, of course, but then, this is a strange business."

"It is, indeed," I agreed ruefully. "Well, go on."

"I had an idea, Ewart, that we should find some sort of wireless telegraphy at the bottom of this business. I had almost made up my mind that we had stumbled across the path of some inventor who was working with a new form of wireless transmission. I felt that in that way we might account for Miss McLeod's blindness and the blindness of the dog. It also seemed to hold good as to the disappearance of Sholto. The inventor hears of the extraordinary effect of his invention, and is afraid he will get into a mess if it is found out.

The yacht to experiment from fitted in beautifully. But now all that's knocked on the head."

"Why?" I asked. "It seems to me, Garnesk, that you are doing all the thinking in this affair, as if you had been used to it all your life.

Your only trouble is that you're too modest. I take it that because you didn't see the yacht when you noticed the green flash you are taking it for granted you were wrong to expect it. I must say, old chap, I think you've done thundering well, as the General would put it, and even if you are prepared to admit your theory has been knocked on the head I'm not--at any rate, not until I have a jolly good reason. Yet it doesn't seem to matter much what I say or do if I'm going to faint like a girl at the first sign of danger. If you hadn't come to my rescue I might still be lying there waiting to come round, or something," I finished in disgust.

My companion looked at me thoughtfully.

"Ewart," he said, and solemnly shook his head, "you have brought me to the very thing that made me say my theory was exploded."

"What thing?" I asked. "Surely my fainting can't have made any difference to conclusions you had already come to?"

"But then you see," my friend replied, "you didn't faint. And if I had not seen you were in difficulties you would probably never have recovered."

"Didn't faint?" I exclaimed. "Well, I don't know what the medical term for it is, and I daresay there are several technical phrases for the girlish business I went through. That idea of being dumb was simply imagination, but I a.s.sure you it was just what I should call a fainting fit."

"I don't want to alarm you if you're not feeling well," he began apologetically.

"Go on," I urged. "I'm as fit as I ever was."

"Well," the young specialist responded, in a serious tone, "if you want to know the truth, Ewart, you were suffocated."

"Suffocated!" I shouted, jumping to my feet. "What in heaven's name do you mean?"

"I can't tell you exactly what I mean because I don't know, but yours was certainly not an ordinary fainting fit. To put the whole thing in non-medical terms, you were practically drowned on dry land!"

I sat down again--heavily at that. Should we never come to an end of these mysterious attacks which were hurled at us in broad daylight from nowhere at all?

"I'm not sure that you hadn't better rest before we go into this fully, Ewart," Garnesk remarked doubtfully. "You're not by any means as fit as you've ever been, in spite of your emphatic a.s.surance."

"Tell me what you think, why you think it, and what you feel we ought to do. Why, man, Myra might have been here alone, with no one to rescue her and--and----"

"Quite so," said Ewart sympathetically. "So you must comfort yourself with the knowledge that it may be a great blessing that she has temporarily lost her sight. Now, I say you didn't faint, because, medically, I know you didn't. For the same reason I say you were suffocating as surely as if you had been drowning. Hang it, my dear chap, it's my line of business, you know. I can't account for it, but there is the naked fact for you."

"How does this affect your previous conclusions?" I asked. "Before you tell me what you think brought on this suffocation I should like to hear why you give up your theory."

"Simply because no wireless, or other electric current, could have that effect upon you. If you had had an electric shock in any of its many curious forms I could have said it bore me out; but, you see, it's impossible. And, as I refuse to believe that we are continually b.u.mping into new mysteries which have no connection with each other, it follows that if this suffocation was not caused by the supposed wireless experiments, the other can't have been either."

"I'm not making the slightest imputation on your medical knowledge," I ventured, "but are you absolutely certain that you are not mistaken?"

"My dear fellow," he laughed, "for goodness sake don't be so apologetic. I can quite see that you find it difficult to believe. But I am prepared to swear to it all the same. For one thing, the symptoms were unmistakable; for another, it seems impossible that we should both faint at exactly the same time and place for no reason at all."

"You didn't faint too, surely?" I cried.

"No," he admitted, "but we might very easily have been suffocated together--smothered as surely as the princes in the Tower. When I saw you were in difficulties I shouted to you. Obviously you didn't hear me. I naturally didn't wait to see what would happen to you; I cleared down the cliff, and sprinted to you as fast as I could. When I came to within about twenty yards of you I found a difficulty in breathing. I went on for a couple of paces, and realised that the air was almost as heavy as water. So I rushed back, undid my collar, took a deep breath; and bolted in to you, picked you up, and carted you here. _Voila!_ But I very nearly joined you on the ground, and then we would never have regained consciousness, either of us. I applied the simplest form of artificial respiration to you, dowsed your head, and now you're all right. On the whole, Ewart, we can consider ourselves very well out of this latest adventure."

"What you're really telling me," I pointed out gratefully, "is that you saved my life at the risk of your own. I'm no good at making speeches, or anything of that sort, Garnesk, but I thank you, if you know what that means. And Myra will----"

"Not a word to her, Ewart," my companion interrupted eagerly.

"Whatever you do, don't on any account worry that poor girl with this new complication. Anything on earth but that."

"No," I agreed; "you're right there. Myra must be kept in the dark."

"Yes," he replied, with a look of relief. "It might have a serious effect on her chances of recovery if she had this additional worry.

And I don't think it would be advisable to tell the old man either. I think we had better keep it to ourselves absolutely. Tell no one, Ewart, except your friend when he comes."

"Very well," I answered, for I was very anxious to spare both Myra and her father from the knowledge of any further trouble. "I'll tell Dennis when he comes, but otherwise it is our secret."

"Good," said Garnesk. "Now put your coat on, old chap, and we'll stroll back to the house."

I got up and b.u.t.toned my collar, retied my bow, and slipped into my jacket. I was rather uncomfortably damp, and I felt a bit shaky and queer, and decided that I could do with a complete rest from the mysteries of the green ray. But the subject remained uppermost in my mind, and my tired brain still strove to unravel the tangled threads of the puzzle.

"By the way," I said, as we walked slowly up to the house, "you have not yet explained what there was in my remark about the sunlight that made you think of the yacht."

"Well," he replied, "you see I had an idea that perhaps they might come here when the gorge, through which the river flows, was flooded with light, so that they could see if any strange effects were produced. But that suffocation was not brought about by any electrical experiment, and I am beginning to be afraid that, after all, we may be up against some strange natural phenomena, some terrible combination of the forces of Nature, which has not yet been observed, or at any rate recorded."

"Why afraid?" I asked, for although I had been glad to believe that we were faced with a problem which would prove to have a human solution, the revulsion had come, and I should have welcomed the knowledge that some weird, freakish application of natural power might be held accountable.

"Afraid?" queried Garnesk, with a note of surprise. "I am very often afraid of Nature. She is a devoted slave, but a cruel mistress. I don't think that I should ever be very much scared by a human being, even in his most fiendish aspect, but Nature--I tell you, Ewart, there are things in Nature that make me shudder!"

"Yes," I agreed heavily, "you're right, of course. That's how I have felt for the past twenty-four hours. It was a tremendous relief to me to feel that we were men looking for men. But the last few minutes I have had an idea that it would be comforting to explain it all out of a text-book of physics. Still, you're right. It is better far to be men fighting men than to be puny molecules tossed in the maelstrom of immutable power which created the world, and may one day destroy it."

"I'm glad you agree," he said simply. "You see you could not possibly live for a second in electrically produced atmosphere which was so thick that you couldn't hear yourself speak. Death would be instantaneous. It couldn't have been our unknown professor's wireless experiments after all. Yet it seems impossible that a sudden new power should crop up suddenly at one spot like this. Imagine what would happen if this had occurred in a city, in a crowded street. Hundreds would have been stricken blind, then hundreds would have been suffocated. Vehicles would have run amok, and the result would have been an indescribable chaos of the maimed, mangled and distraught. A flash like this green ray (which blinded Miss McLeod and her dog, deluded the General, and nearly suffocated us) at the mouth of a harbour, say, the entrance to a great port--Liverpool, London, or Glasgow--would be responsible for untold loss of life. If this terrible phenomenon spread, Ewart, it would paralyse the industry of the world in twenty-four hours. If it spread still farther the face of the globe would become the playing-fields of Bedlam in a moment. Think of the result of this everywhere! Some suffocated, some blinded, and millions probably mad and sightless, stumbling over the bodies of the dead to cut each other's throats in the frenzy of sudden imbecility."

"Don't, Garnesk," I begged. "It won't bear thinking about. We have enough troubles here to deal with without that!"

"Yes," my companion admitted, "we need not add to them by any idle conjectures of still more hideous horrors to come. But it is an interesting, if terrible speculation. And it means one thing to us, Ewart, of the very greatest importance. We must solve the riddle somehow."

"You mean," I cried, as I realised the tremendous import of his words--"you mean that the sanity of the universe may rest with us! You mean that if we can solve this riddle we, or others, may be able to devise some means of prevention, or at least protection? You mean that we are in duty bound to keep at this night and day until we find out what it is?"

"That is just what I do mean," he replied seriously. "It is a solemn duty; who knows, it may be a holy trust. Ewart, we agree to get to the bottom of this? We have agreed once, but are we still prepared to go on with this now that we know we may be crushed in the machinery that controls the solar system and lights the very sun?"