"Whatever it is, we've stumbled on something of real importance this

time. We must find out what it is and show it up at once."



"I hope you'll take care," said Myra anxiously. "I shouldn't mind so

much if I could be with you to help, but it's dreadful to sit here and

know you are in danger and not be able to do anything at all."



"I'm very glad you can't, darling," I said heartily, as I threw my arm

round her shoulders. "I don't want you to come rushing into these

dangers, whatever they may be. In a way I am glad you are not able to

join us, because I know how difficult it would be to stop you if you

were."



"I suppose this is all one affair," she said doubtfully. "You don't

think this is something quite different from the green ray? It might

be two quite separate things, you know."



"I don't think we are likely to meet with two such interesting

problems in such a remote locality unless they are connected with each

other, Miss McLeod, and especially as everything else apart from the

photograph of Baron von Guernstein points to Fuller as the culprit. I

think we can take it that in solving one mystery we provide the

solution to the other."



"I quite agree with you, Dennis," I said, "but what I am worrying

about now is, what we are going to do."



"The first thing you must do is to dress for dinner, and not let

anyone imagine there is anything untoward about," Myra advised. "And

please don't tell father you have been lunching with one of the

Kaiser's principal spies, if that's what the Baron's title really

means. I would much rather you said nothing to him at all about it for

the present, and in any case you must have something definite in mind

as to your plans before you put the matter to him. If you tell him you

don't know what to do about it he will be in a dreadful state. He is

very far from well, and all this business has told on him dreadfully."



"That is very excellent advice, Miss McLeod," Dennis agreed warmly.

"Ronald, we'll go and disguise ourselves as ordinary, undisturbed

human beings and hide our fears and doubts behind the breastplate of

a starched shirt. Come along."



So Dennis dragged me away, and then, realising his indiscretion,

allowed me to return to my fiancee "just for two minutes, old

fellow."



Dinner was a curious meal, though not quite so strange as the meal the

General and I had together the night, less than a week before, that

Myra lost her sight.



I hope I shall never live through a week like that again. Even now, as

I look back, I cannot believe that it all happened in seven days. It

still seems to have been something like seven months at the very

least.



We had one thing in our favour as we sat down to the table; we all had

a common object in view. We were each of us determined to forget the

green ray for a moment. Fortunately the old man took an immediate

fancy to Dennis and that brightened me considerably. There are few

things so pleasant as to see those whose opinion you value getting on

with your friends. Only once, and that after Mary McNiven had come to

take poor Myra away, did the subject of the green ray crop up.



"Mr. Burnham knows about it all, I suppose?" the General asked.



"I've told him everything, and Garnesk and I went over the whole thing

with him before the train went."



"Good!" said the old man emphatically. "Excellent fellow

Garnesk--excellent; in fact, I don't know when I've met such a

thundering good chap. No new developments, I suppose?"



I hesitated. I could not have brought myself to lie to him, and in

view of the startling complications with which we had so recently been

confronted, I was at a loss for an answer. Dennis came to my rescue

just in time.



"I think Ron's difficulty is in defining the word 'developments,'

General," said he. "If we said there were developments it would

naturally convey the impression that we had something definite to

report. I think perhaps the best way to put it would be that we

believe we are getting on the right scent, by the simple process of

putting two and two together and making them four. We hope to have

something very decided to tell you in a day or two."



"I shall be glad to hear something, I can assure you," said the old

man, "but in the meantime we will try to forget about it. You have had

a tiring journey, Mr. Burnham, followed by a strange initiation into

what is probably a new sphere of life altogether--the sphere of

mysteries and detectives, and so forth. No, Ronald, we'll give Mr.

Burnham a rest for to-night."



But just as I was congratulating myself that we had escaped from the

painful necessity of putting him off with an evasive answer, if not a

deliberate lie, the butler entered and announced that he had shown

Mr. Hilderman into the library.



"Well, as we are ready, we had better join him," said the old man, and

we adjourned to the other room.



Now if Hilderman should by any tactless remark betray our strange

experience in the afternoon there would be the devil to pay. I

followed the General into the library, beckoning to the American with

a warning finger on my lip. He saw at once what I meant, fortunately,

and held his tongue, and we all talked of general matters for some

little time. Then Hilderman took the bull by the horns.



"As a matter of fact, General," he announced boldly, "I ran over to

have a word with Mr. Ewart about a certain matter which is interesting

us all. I don't suppose you wish me to worry you with details at the

moment?"



"I should be very glad to hear what you have to tell us, Mr.

Hilderman, but unfortunately I--er--I have a few letters I simply

must write, so I hope you will excuse me. My daughter is in the

drawing-room, so perhaps you fellows would care to join her there. Her

counsel will be of more use to you than mine in your deliberations, I

have no doubt."



However, when we looked for her in the drawing-room Myra was not

there, and I found her in her den.



"Why not bring him in here?" she asked. "He won't bite, and it will

be more conducive to a free and easy discussion. I should like to

hear what he has to say for himself in view of his running away this

afternoon, and I shouldn't feel comfortable in the drawing-room with

this shade on. In here I feel that he must just put up with any

curiosities he meets."



So we made ourselves comfortable in the den, and Hilderman sat in a

chair by the window.



"Of course, you know what I have come to speak about, Mr. Ewart," he

began at once. "You must have thought my conduct this afternoon was

very strange--very unsportsmanlike, to say the least."



"Oh, I don't know," I replied as lightly as I could. "It was a very

strange affair, and it rather called for strange conduct of one sort

or another."



"Still, you must have thought it cowardly to run away as quickly as I

could," he insisted.



"It was some time before we even noticed you had left us," I laughed,

"and then, I confess, I couldn't quite make out where you had got to

or why you had gone."



"As a matter of fact we were rather scared," Dennis put in. "We

searched for you in the river."



"It sounds a very cowardly confession to make," Hilderman admitted,

"but I went back to the landing-stage, got into my boat, and cleared

off as quickly as I could. I must ask you to believe that I was under

the impression that it would be best for us all that I should. But my

idea proved to be a bad one and nothing came of it. So here I am to

ask you if you have learned anything or have anything to suggest."



"I'm afraid we're more at a loss than ever now," I admitted. "The

further we get with this thing the less we seem to know about it,

unfortunately."



Hilderman was exceedingly sympathetic, and though he made numerous

suggestions he was as puzzled as we were ourselves. I had some

difficulty in defining his attitude. We knew as much as was sufficient

to hang his friend "Fuller," but I could not make up my mind whether

he really was a friend of von Guernstein's or not. It was a small

thing that decided me. On an occasionable table beside the American

lay a steel paper-knife, a Japanese affair, with a carved handle and a

very sharp blade. Hilderman picked up the knife and toyed with it.



"I should be careful with that, Mr. Hilderman," I advised. "That is a

wolf in sheep's clothing; it's exceedingly sharp."



"Oh, yes!" cried Myra. "If you mean my paper-knife, it ought not

really to be used as a paper-knife at all, the point is like a needle.

I must put it away or hang it up as an ornament."



The American laughed and laid the knife down again on the table, and

we resumed our discussion. Both Dennis and I knew that we must be very

careful to conceal our suspicions, but at the same time we did our

best to reach some sort of conclusion with regard to Hilderman

himself.



"And, I suppose, until you have searched about the Saddle," he

remarked, "you will be no further on as to who stole Miss McLeod's

dog. It seems to me that the dog was taken by the man who wished to

conceal an illicit still, and the green flash, or green ray, or

whatever you call it, is simply a manifestation of some strange

electrical combination in the air."



"I'm afraid we shall have to leave it at that," I said with an

elaborate sigh of regret.



"Not when you have Mr. Burnham's distinguished powers of deduction to

assist you, surely, Mr. Ewart?" said Hilderman, and waited for an

answer.



"Flukes are not very consistent things, I fear," Dennis supplied him

readily, "and if we are to make any progress we shall hardly have time

for idle speculation."



"Fortune might continue to favour you," the American persisted. "Don't

you think it's worth trying?"



"I'm afraid not," said Dennis, with a laugh that added emphasis and

conviction to his statement.



"By the way," Myra suggested, "I don't know if anybody would care for

a whisky and soda or anything. I won't have drinks served in here, but

if anybody would like one, you know where everything is, Ron. I always

say if anyone wants a drink in my den they can go and get it, and

then I know they really like being in the den. You see I'm a woman,

Mr. Hilderman," she laughed.



"I must say I think the idea of refreshment would not enter the head

of anyone who had the pleasure of your company here, Miss McLeod,

unless you suggested it yourself."



We laughed at the rather heavy compliment, and I went into the

dining-room to fetch the decanters, syphons and glasses.



"I'll help you to get them," called Dennis, and followed me out of the

room.



"Well?" I asked as soon as we reached the other room. "What do you

make of it?"



"I'm not sure," Dennis admitted. "I'm puzzled. I shouldn't be

surprised if he turned out to be a Government secret service man

keeping an eye on Fuller-von-Guernstein, and that when he has quite

made up his mind that the mystery of the green ray is connected with

his own business he will show his hand."



"Something of the same sort occurred to Garnesk," I said. "Well,

at present we'd better avoid suspicion and go back before he thinks

we're holding a committee meeting."



So I led the way to the den. I was walking carefully and slowly,

because I was unaccustomed to carrying trays of glasses and things,

and consequently I made no noise. I pushed the door open with my

shoulder, Dennis following with a couple of syphons, and as I did so

I chanced to glance upwards.



In a large mirror which hung over the fireplace I saw the reflection

of Hilderman's face, knitted in a fierce frown, gazing intently at

some object which was outside my view. Myra was talking, though what

she was saying I did not notice. I went into the room and put the tray

on the big table, and as I filled the glasses I looked round casually

to see what Hilderman had been looking at. Lying on the sofa on which

Myra was sitting was the copy of the Pictures, open at the page

bearing the incriminating photograph!



I mixed Hilderman's drink according to his instructions--for by this

time he had entirely recovered his equanimity--and handed it to him.

As I did so I happened to look in the direction of the small table

beside him. Myra's Japanese paper-knife was still there, but the point

had been stuck more than an inch into the mahogany top of the table. I

turned away quickly, with a laughing remark to Myra, which did not

seem to raise any suspicion at the time, though I have no recollection

now what it was I said.



A few moments afterwards I quietly and unostentatiously slipped out of

the room. Surely there could be no doubt about it now. The whole thing

was obvious. Hilderman had noticed the paper, jumped to the conclusion

that we suspected everything, and in the sudden access of baffled rage

had picked up the paper-knife and stabbed it into the table.



There was only one possible reason for that--Hilderman was an enemy.

In that case, I thought, he has come here to try and find out how much

we know and to keep an eye on us. Possibly he might be attempting to

keep us there so that Fuller could get up to some satanic trick

elsewhere. I decided to act at once. I turned back to the den and put

my head round the door.



"Will you people excuse me for a bit?" I said lightly. "The General

wants me." And with that I left them. I had almost asked Hilderman not

to go till I came back, but I was afraid it might sound suspicious to

his acute ears. I hardly knew what to do. I should have liked to have

been able to speak with Dennis, if only for a moment. Indeed, I am

quite ready to confess that just then I would have given all I

possessed for ten minutes' conversation with my friend. I stole

quietly out of the house, and thought furiously.



If Hilderman wanted to keep us from spying on Fuller, where was

Fuller? Would I be wiser to wait and try to keep an eye on Hilderman,

or was my best plan to ignore him and try and locate his German

friend? I decided on the latter course. I went back and wrote a short

note to Dennis and slipped it inside his cap.



"I'm convinced they are both enemies. Take care of Myra. I may be out

all night. Don't let her worry about me; I may not be back for some

time, but I shall come back all right.--R."



I left this for my friend, knowing that sooner or later he would find

it, and went down to the landing-stage. The Baltimore II. and Myra's

boat, the Jenny Spinner, were drawn up alongside, and I realised

that if I took the Jenny I should be raising Hilderman's suspicions

at once. Anchored a little way out was another small motor-boat--the

first the General had--which Myra had also called after a trout

fly--the Coch-a-Bondhu--though the play upon words was lost on most

people. The boat was still in constant use, and Angus and Hamish

continually went into Mallaig and Glenelg in it to collect parcels and

so on. I ran to the petrol shed, and got three tins of Shell, put them

in the dinghy and pushed out to the Bondhu, climbed on board,

sounded the tank, filled it up, and started out across the Loch. I can

only plead my anxiety to get well out of sight and hearing before

Hilderman should think of leaving the house, as an excuse for my

lamentable thoughtlessness on this occasion. Indeed, it was not till

long afterwards that I realised I had forgotten to anchor the dinghy,

and I left it, just as it was, to drift out to sea on the tide.



I made all the pace I could and reached the other side in about twenty

minutes. I was sadly equipped for an adventurous expedition! I had no

flask to sustain me in case of need, no weapon in case I should be

called to defend myself; I was wearing a dinner-jacket, no hat, and a

pair of thin patent-leather pumps!



I ran the boat right in shore, heedless of the danger to the

propeller, in a small sandy cove round the point, so that I was hidden

from Glasnabinnie. Then I realised that I had been a little too

precipitate in my departure. There was no anchor-chain on board, and

the painter was admirably suited for making fast to pier-heads and

landing-stages at high tide, but was nothing like long enough to

enable me to make the craft secure on short. However, I dragged her as

far up as I could, and prayed that I might be able to return before

the tide caught her up and carried her away. In those circumstances I

should have been stranded in the enemy's country, by no means a

pleasing prospect!



Having done the best I could for Myra's faithful motor-boat, I made my

way round the hill, climbing cautiously upwards all the time, my

dinner-jacket carefully buttoned in case a gleam of moonlight on my

shirt-front should give me away at a critical moment. It was a rocky

and difficult climb, and I soon regretted that I had not taken the

bridle path to Glasnabinnie and made my way boldly up the bed of the

burn. However, it was too late to turn back, and eventually, after one

or two false steps and stumbles, I succeeded in reaching a spot from

which I could obtain a good view of the hut. No, there was no light

there, no sign of movement at all. I decided to work my way round to

the other side and then, if I continued to get no satisfaction, to

descend to the house. The windows of the hut, or smoking-room, as the

reader will no doubt remember, extended the whole length of the

structure; and surely, I thought, if there were a light in the place

it would be bound to be visible. I edged round the face of a steep

crag, floundered across the stream between the two falls, getting

myself soaked above the knees as I did so, and crouched among the

heather on the other side of the building. No, there was no one there,

the place was deserted. I knelt down and peered about me listening

intently.



Not a sound greeted my expectant ear save the incessant rumble of the

falls. Then as I turned my attention to the house itself and looked

down the course of the burn to Glasnabinnie, I could scarcely suppress

a cry of astonishment. For there below me, moving to and fro between

the house and the hut, was a constant procession of small lights, like

a slowly moving stream of glow-worms, twenty or thirty yards apart. I

was rooted to the spot. What could it mean? Was this another weird

natural manifestation, or was it, as was much more likely, a couple of

dozen men bearing lights? Yes, that was it, men bearing lights--and

what else besides? Men don't climb up and down steep watercourses in

the night for the sake of giving an impromptu firework display to an

unexpected visitor, I told myself. There was only one thing to do, and

that was to investigate the matter and chance what might happen to me.

I crept down to the hut, and lay on my face among the heather and

listened. Here and there a mumble of voices, now and then a subdued

shout, apparently an order to be carried out by the mysterious

light-bearers, broken occasionally by the shrill call of a gull,

conveyed nothing to me that I could not see. I looked up at the hut.

No, there was no one there, and the windows were not screened, because

I could see the moonlight streaming through the far side. Yet, surely,

the hut must be their objective, I thought. Where else could they be

going to? Fascinated, I crawled on my hands and knees till I could

touch the walls of the smoking-room by putting out my arm. I heard a

great commotion coming, it seemed, from the very ground beneath my

feet.



I laid my ear to the ground and listened. The noise grew louder, and

the voices seemed to be shouting against a more powerful sound--the

waterfall, possibly. I thought perhaps the floor of the hut would give

me more opportunity to locate the source of the disturbance. I threw

caution to the winds and slipped through the wide windows into the

room. I moved as carefully as I could, however, once my feet found the

floor, for if there should be anyone below they would probably hear me

up above. I turned back the carpet in order to hear more distinctly,

and as I did so I noticed a rectangular shaft of light which trickled

through the floor. There was a trap-door. I knelt down and lifted it

cautiously by a leather tab which was attached to one side of it and

peered through. I can never understand how it was I did not drop that

hatch again with a self-confessing crash when I realised the

extraordinary nature of the sight that greeted my eyes. There was I in

the smoking-hut of a peaceful American citizen, where only a few hours

before I had spent a pleasant hour in friendly conversation, and now I

was lying on the edge of the entrance to a great cavern.



Below me there was a confused mass of machinery and men. Some were

working on scaffolding, others were many feet below. The nearest of

them was so close to me that I could have leaned down and laid my hand

on his head. I tried to make out what they were doing, but except that

they were dismantling the machinery, whatever it might be, I could

make nothing of it. I watched them breathlessly, trembling lest at any

moment one of them should look up and detect my presence.



The place was lighted by electricity, though there were not enough

lamps to illuminate the cavern very brightly, and as my eyes got

accustomed to the lights and shadows I was able to make out the cause

of this.



Evidently there was a turbine engine below, driven by the water from

the falls, which supplied the necessary power. After a moment or two

it dawned on me how the cavern came to be there; it was, or had been,

the course of a hidden river, such as are common enough among the

mountains, but the stream had been diverted, probably by some sort of

landslide, and had left this tumbler-shaped cave, resembling a pit

shaft. Now, I thought, I have only to find out what all this machinery

is for and the whole mystery is solved. I opened the trap a little

further, and allowed my body to hang slightly over the edge.



Then for the first time I saw, to my right, fixed so that it almost

touched the floor of the hut, a great round brass object, mounted on

an enormous tripod, which, again, stood on a platform. In front of

this was a large square thing like a mammoth rectangular condenser,

such as is used for photographic enlarging and other projection

purposes. Had it not been for this condenser I should have taken the

whole thing to be an elaborate searchlight. But, I asked myself, what

would be the good of a searchlight there? Suddenly the whole truth

dawned upon me.



The searchlight must operate through a trap in the wall of the hut

just below the floor. I leaned further in, forgetting my danger in the

intoxication of sudden discovery.



Only a foot or two away from me a man was working on the searchlight.

Carefully taking it to pieces, he was handing the parts to another

man, who was perched on the scaffold below him. He was so close to

me that I could hear him breathing. I was about to wriggle back to

safety when he looked up. He gave a sudden loud shout. I lay there

fascinated. After all, I thought, before they can reach me I can slip

out and edge round the cliff, run down on to the shore, and get away

in the motor-boat. But I had reckoned without my host. Even as the man

shouted, and the others left their work to see what was the matter,

Fuller dashed out from behind the platform, gave one terrified look at

me, and, flinging himself at the wall of the cavern, threw all his

weight on a rope which dangled there. I scuttled to my feet, intending

to make a bolt for it. But the boards shivered beneath me, and, before

I could realise what was happening, I found myself hurtling through

the air to the floor of the cavern below.