I could have yelled for joy. We were about to learn something of the Blind Spot—something that might help us to save Harry, and Chick, and the professor!

Ariadne seemed to know that a great deal depended upon what she was about to tell us. She deliberately sat down, and rested her chin upon her hand, as though determining upon the best way of telling something very difficult to express.

As for Charlotte, Jerry, and myself, we managed somehow to restrain our curiosity enough to keep silence. But we could not help glancing more or less wonderingly at our visitor. Presently I realised this, and got up and walked quietly about, as though intent upon a problem of my own.

Which was true enough. I had come to a very startling conclusion—I, Hobart Fenton, had fallen in love!

What was more, this affection of the heart had come to me, a very strong man, just as an affection of the lungs is said to strike such men—all of a sudden and hard. One moment I had been a sturdy, independent soul, intent upon scientific investigation, the only symptoms of sentimental potentialities being my perfectly normal love for my sister and for my old friend. Then, before my very eyes, I had been smitten thus!

And the worst part of it was, I found myself ENJOYING the sensation. It made not the slightest difference to me that I had fallen in love with a girl who was only a step removed from a wraith. Mysteriously she had come to me; as mysteriously she might depart. I had yet to know from what sort of country she had come!

But that made no difference. She was HERE, in the same house with me; I had held her hands; and I knew her to be very, very real indeed just then. And when I considered the possibility of her disappearing just as inexplicably as she had come—well, my face went cold, I admit. But at the same time I felt sure of this much—I should never love any other woman.

The thought left me sober. I paused in my pacing and looked at her. As though in answer to my gaze she glanced up and smiled so affectionately that it was all I could do to keep from leaping forward and taking her right into my arms.

I turned hastily, and to cover my confusion I began to hum a strain from the part of “Faust” to which I have referred. I hummed it through, and was beginning again, when I was startled to hear this from the girl: “Oh, then you are Hobart!”

I wheeled, to see her face filled with a wonderful light.

“Hobart,” she repeated, as one might repeat the name of a very dear one. “That—that music you were humming! Why, I heard Harry Wendel humming that yesterday!”

I suppose we looked very stupid, the three of us, so dumbfounded that we could do nothing but gape incredulously at that extraordinary creature and her equally extraordinary utterance. She immediately did her best to atone for her sensation.

“I'm not sure that I can make it clear,” she said, smiling dubiously, “but if you will use your imaginations and try to fill in the gaps in what I say you may get a fair idea of the place I have come from, and where Harry is.”

We leaned forward, intensely alert. I shall never forget the pitiful eagerness in poor Charlotte's face. It meant more to her, perhaps, than to anyone else.

At the precise instant I heard a sound, off in the breakfast room. It seemed to be a subdued knocking, or rather a pounding at the door.

Frowning at the interruption, I stepped through the dining-room into the breakfast room, where the sounds came from. And I was not a little puzzled to note that the door to the basement was receiving the blows.

Now I had been the last to visit the basement and had locked the door—from force of habit, I suppose—leaving the key in the lock. It was still there. And there is but one way to enter that basement: through this one door, and no other.

“Who is it?” I called out peremptorily. No answer; only a repetition of the pounds.

“What do you want?”—louder.

“Open this door, quick!” cane a muffled reply.

The voice was unrecognisable. I stood and thought quickly; then shouted:

“Wait a minute, until I get a key!”

I motioned to Charlotte. She tip-toed to my side. I whispered something in her ear; and she slipped off into the kitchen, there to phone Miss Clarke and warn her to notify her colleagues at once. And so, as I unlocked the door, I was fortified by the knowledge that I would be assisted by the combined mind-force of a score of highly developed intellects.

I was little surprised, a second later, to see that the intruder was Rhamda Avec. What reason to expect anyone else?

“How did you get down there?” I demanded. “Don't you realise that you are liable to arrest for trespass?”

I said it merely to start conversation but it served only to bring a slight smile to the face of this professed friend of ours, for whom we felt nothing but distrust and fear.

“Let us not waste time in trivialities, Fenton,” he rejoined gently. He brushed a fleck of cobweb from his coat. “By this time you ought to know that you cannot deal with me in any ordinary fashion.”

I made no comment as, without asking my leave or awaiting an invitation, he stepped through into the dining-room and thence into the parlour. I followed, half tempted to strike him down from behind, but restrained more by the fact that I must spare him than from any compunctions. Seemingly he knew this as well as I, he was serenely at ease.

And thus he stood before Jerome and Ariadne. The detective made a single exclamation, and furtively shifted his coat sleeves. He was getting that infernal breast gun into action. As for Ariadne, she stared at the new arrival as though astonished at first.

When Charlotte returned, a moment later, she showed only mild surprise. She quietly took her chair and as quietly moved her hand so that the gem shone in full view of our visitor.

But he gave her and the stone only a single glance, and then rested his eyes upon our new friend. To my anxiety, Ariadne was gazing fixedly at him now, her expression combining both agitation and a vague fear.

It could not have been due entirely to his unusual appearance; for there was no denying that this grey-haired yet young-faced man with the distinguished, courteous bearing, looked even younger that night than ever before. No; the girl's concern was deeper, more acute. I felt an unaccountable alarm.

From Ariadne to me the Rhamda glanced, then back again; and a quick satisfied smile came to his mouth. He gave an almost imperceptible nod. And, keeping his gaze fixed upon her eyes, he remarked carelessly:

“Which of these chairs shall I sit in, Fenton?”

“This one,” I replied instantly, pointing to the one I had just quit.

Smiling, he selected a chair a few feet away.

Whereupon I congratulated myself. The man feared me, then; yet he ranked my mentality no higher than that! In other words, remarkably clever though he might be, and as yet unthwarted, he could by no means be called omnipotent.

“For your benefit, Mr. Jerome, let me say that I phoned Miss Fenton and her brother a few days ago, and urged them to give up their notion of occupying this house or of attempting to solve the mystery that you are already acquainted with. And I prophesied, Mr. Jerome, that their refusal to accept my advice would be followed by events that would justify me.

“They refused, as you know; and I am here tonight to make a final plea, so that they may escape the consequences of their wilfulness.”

“You're a crook! And the more I see of you, Avec, the more easily I can understand why they turned you down!”

“So you too, are prejudiced against me. I cannot understand this. My motives are quite above question, I assure you.”

“Really!” I observed sarcastically. I stole a glance at Ariadne; her eyes were still riveted, in a rapt yet half-fearful abstraction, upon the face of the Rhamda. It was time I took her attention away.

I called her name. She did not move her head, or reply. I said it louder: “Ariadne!”

“What is it, Hobart?”—very softly.

“Ariadne, this gentleman possesses a great deal of knowledge of the locality from which you came. We are interested in him, because we feel sure that, if he chose to, he could tell us something about our friends who—about Harry Wendel.” Why not lay the cards plainly on the table? The Rhamda must be aware of it all, anyhow. “And as this man has said, he has tried to prevent us from solving the mystery. It occurs to me, Ariadne, that you might recognise this man. But apparently—”

She shook her head just perceptibly. I proceeded:

“He is pleased to call his warning a prophecy; but we feel that a threat is a threat. What he really wants is that ring.”

Ariadne had already, earlier in the hour, given the gem several curious glances. Now she stirred and sighed, and was about to turn her eyes from the Rhamda to the ring when he spoke again; this time in a voice as sharp as a steel blade:

“I do not enjoy being misunderstood, much less being misrepresented, Mr. Fenton. At the same time, since you have seen fit to brand me in such uncomplimentary terms, suppose I state what I have to say very bluntly, so that there may be no mistake about it. If you do not either quit this house, or give up the ring—NOW—you will surely regret it the rest of your lives!”

From the corner of my eye I saw Jerome moving slowly in his chair, so that he could face directly towards the Rhamda. His hands were ready for the swift, upward jerk which, I knew, would stifle our caller.

As for my sister, she merely turned the ring so that the gem no longer faced the Rhamda; and with the other hand she reached out and grasped Ariadne's firmly.

Avec sat with his two hands clasping the arms of his chair. His fingers drummed nervously but lightly on the wood. And then, suddenly, they stopped their motion.

“Your answer, Fenton,” in his usual gentle voice. “I can give you no more time,” I did not need to consult Charlotte or Jerome. I knew what they would have said.

“You are welcome to my answer. It is—no!”

As I spoke the last word my gaze was fixed on the Rhamda's eyes. He, on the other hand, was looking towards Ariadne. And at the very instant an expression, as of alarm and sorrow, swept into the man's face.

My glance jumped to Ariadne. Her eyes were closed, her face suffused; she seemed to be suffocating. She gave a queer little sound, half gasp and half cry.

Simultaneously Jerome's hands shot into the air. The room shivered with the stunning report of his breast gun. And every pellet struck the Rhamda and burst.

A look of intense astonishment came into his face. He gave Jerome a fleeting glance, almost of admiration; then his nostrils contracted with pain as the gas attacked his lungs.

Another second, and each of us were reeling with the fumes. Jerome started toward the window, to raise it, then sank back into his chair. And when he turned round—

He and I and Charlotte saw an extraordinary thing. Instead of succumbing to the gas, Rhamda Avec somehow recovered himself. And while the rest of us remained still too numbed to move or speak, he found power to do both.

“I warned you plainly, Fenton,” as though nothing in particular had happened. “And now see what you have brought upon the poor child!”

I could only roll my head stupidly, to stare at Ariadne's now senseless form.

“As usual, Fenton, you will blame me for it. I cannot help that. But it may still be possible for you to repent of your folly and escape your fate. You are playing with terrible forces. If you do repent, just follow these instructions”—laying a card on the table—“and I will see what I can do for you. I wish you all good night.”

And with that, pausing only to make a courtly bow to Charlotte, Rhamda Avec turned and walked deliberately, dignifiedly from the room, while the two men and a woman stared helplessly after him and allowed him to go in peace.