After giving me the letter, and receiving my assurance that it would be safely delivered, Sir Digby's spirits seemed somewhat to revive.

He chatted in his old, good-humoured style, drank a whisky and soda, and, just before one o'clock, let me out, urging me to descend the stairs noiselessly lest the hall-porter should know that he had had a visitor.

Time after time I had questioned him regarding his strange reference to his successor, but to all my queries he was entirely dumb. He had, I recollected, never been the same since his return from a flying visit to Egypt.

"The future will, no doubt, astound you, but I know, Royle, that you are a man of honour and of your word, and that you will keep your promise at all hazards," was all he would reply.

The secrecy with which I had entered and left caused me considerable curiosity. Kemsley was one of those free, bluff, open-hearted, open-handed, men. He was never secretive, never elusive. I could only account for his curious, mystifying actions by the fact that the reputation of a woman was at stake—that he was acting for her protection.

And I was to meet that woman face to face in eight days' time!

As I walked towards Gloucester Road Station—where I hoped to find a taxi—all was silence. At that hour the streets of South Kensington are as deserted as a graveyard, and as I bent towards the cutting wind from the east, I wondered who could be the mysterious woman who had broken up my dear friend's future plans. Yet he bore her no malice. Some men's temperaments are really curious.

Beneath a street-lamp I paused and looked at the superscription upon the envelope. It ran:

The initial K! Was the lady Digby's wife? That was the suspicion which at once fell upon me, and by which I became convinced.

At half-past one o'clock I let myself into my own flat in Albemarle Street. The faithful Haines, who had been a marine wardroom servant in the navy before entering my employ, was awaiting me.

"The telephone bell rang ten minutes ago, sir," he said. "Sir Digby Kemsley wishes to speak to you."

"Very well!" I replied. "You can go to bed."

The man placed my tray with whisky and soda upon the little table near my chair, as was his habit, and, wishing me good-night, retired.

I went to the telephone, and asked for Digby's number.

After a few seconds a voice, which at first I failed to recognise, replied to mine:

"I say, Royle; I'm so sorry to disturb you, old chap, but could you possibly come back here at once?"

"What?" I asked, very surprised. "Is it so very important? Can't it wait till to-morrow?"

"No, unfortunately it can't. It's most imperative that I should see you. Something has happened. Do come!" he begged. "But don't attract attention—you understand!"

"Something happened!" I echoed. "What?"

"That woman. Come at once—do, there's a good fellow. Will you—for my sake and hers?"

The mention of the woman decided me, so I replied "All right!" and hung up the receiver.

Within half an hour I alighted in Courtfield Gardens and walked up Harrington Gardens to the door of my friend's house, which I saw was already ajar in anticipation of my arrival.

Closing the door noiselessly, in order not to attract the attention of the alert porter who lived in the basement, I crept up the carpeted stairs to the door of the flat, which I found also ajar.

Having closed the door, I slipped into the hall and made my way to the warm, cosy room I had left earlier that night.

The door was closed, and without ceremony I turned the handle.

I threw it open laughingly in order to surprise my friend, but next instant halted in amazement upon the threshold.

I stood there breathless, staring in speechless wonder, and drawing back.

"I'm really very sorry!" I exclaimed. "I thought Sir Digby was here!"

The man who had risen from his chair and bowed when I opened the door was about the same build, but, apparently, a trifle younger. He had iron-grey hair and a pointed beard, but his face was more triangular, with higher cheek-bones, and eyes more brilliant and deeper set.

His thin countenance relaxed into a pleasant smile as he replied in a calm, suave voice:

"I am Sir Digby Kemsley, and you—I believe—are Mr. Edward Royle—my friend—my very intimate friend—are you not?"

"You!" I gasped, staring at him.

And then, for several seconds I failed to articulate any further words. The imposture was so utterly barefaced.

"You are not Sir Digby Kemsley," I went on angrily at last. "What trick is this?"

"No trick whatever, my dear Royle," was the man's quiet reply as he stood upon the hearthrug in the same position in which my friend had stood an hour before. "I tell you that my name is Kemsley—Sir Digby Kemsley."

"Then you assert that this flat is yours?"

"Most certainly I do."

"Bosh! How can you expect me to believe such a transparent tale?" I cried impatiently. "Where is my friend?"

"I am your friend, my dear Royle!" he laughed.

"You're not."

"But did you not, only an hour ago, promise him to treat his successor in the same manner in which you had treated himself?" the man asked very slowly, his high, deep-set eyes fixed upon me with a crafty, almost snake-like expression, an expression that was distinctly one of evil.

"True, I did," was my quick reply. "But I never bargained for this attempted imposture."

"I tell you it is no imposture!" declared the man before me. "You will, perhaps, understand later. Have a cigar," and he took up Digby's box and handed it to me.

I declined very abruptly, and without much politeness, I fear.

I was surveying the man who, with such astounding impudence, was attempting to impose upon me a false identity. There was something curiously striking in his appearance, but what it was I could not exactly determine. His speech was soft and educated, in a slightly higher pitch than my friend's; his hands white and carefully manicured, yet, as he stood, I noted that his left shoulder was slightly higher than the other, that his dress clothes ill-fitted him in consequence; that in his shirt-front were two rare, orange-coloured gems such as I had never seen before, and, further, that when I caught him side face, it much resembled Digby's, so aquiline as to present an almost birdlike appearance.

"Look here!" I exclaimed in anger a few moments later. "Why have you called me over here? When you spoke to me your voice struck me as peculiar, but I put it down to the distortion of sound on the telephone."

"I wanted to see if you recognised my other self," he answered with a smile.

"At this late hour? Couldn't you have postponed your ghastly joke till the morning?" I asked.

"Joke!" he echoed, his face suddenly pale and serious. "This is no joke, Royle, but a very serious matter. The most serious that can occur in any man's life."

"Well, what is it? Tell me the truth."

"You shall know that later."

"Where is Sir Digby?"

"Here! I am Sir Digby, I tell you."

"I mean my friend."

"I am your friend," was the man's response, as he turned away towards the writing-table. "The friend you first met on the Lake of Garda."

"Now, why all this secrecy?" I asked. "I was first called here and warned not to show myself, and, on arrival, find you here."

"And who else did you expect to find?" he asked with a faint smile.

"I expected to find my friend."

"But I am your friend," he asserted. "You promised me only an hour ago that you would treat my successor exactly as you treated me. And," he added, "I am my own successor!"

I stood much puzzled.

There were certain features in his countenance that were much like Digby's, and certain tones in his voice that were the same. His hands seemed the same, too, and yet he was not Digby himself.

"How can I believe you if you refuse to be frank and open with me?" I asked.

"You promised me, Royle, and a good deal depends upon your promise," he replied, looking me squarely in the face. "Perhaps even your own future."

"My future!" I echoed. "What has that to do with you, pray?" I demanded angrily.

"More than you imagine," was his low response, his eyes fixed upon mine.

"Well, all I know is that you are endeavouring to make me believe that you are what you are not. Some evil purpose is, no doubt, behind it all. But such an endeavour is an insult to my intelligence," I declared.

The man laughed a low, harsh laugh and turned away.

"I demand to know where my friend is!" I cried, stepping after him across the room, and facing him again.

"My dear Royle," he replied, in that curious, high-pitched voice, yet with a calm, irritating demeanour. "Haven't I already told you I am your friend?"

"It's a lie! You are not Sir Digby!" I cried angrily. "I shall inform the police that I've found you usurping his place and name, and leave them to solve the mystery."

"Act just as you think fit, my dear old fellow," he laughed. "Perhaps the police might discover more than you yourself would care for them to know."

His words caused me to ponder. At what could he be hinting?

He saw my hesitancy, and with a sudden movement placed his face close to me, saying:

"My dear fellow look—look into my countenance, you surely can penetrate my disguise. It cannot be so very perfect, surely."

I looked, but turned from him in disgust.

"No. Stop this infernal fooling!" I cried. "I've never seen you before in my life."

He burst out laughing—laughed heartily, and with genuine amusement.

His attitude held me in surprise.

"You refuse to be my friend, Royle—but I desire to be yours, if you will allow me," he said.

"I can have no friend whom I cannot trust," I repeated.

"Naturally. But I hope you will soon learn to trust me," was his quiet retort. "I called you back to-night in order to see if you—my most intimate friend—would recognise me. But you do not. I am, therefore, safe—safe to go forth and perform a certain mission which it is imperative that I should perform."

"You are fooling me," I declared.

For a second he looked straight and unflinchingly into my eyes, then with a sudden movement he drew the left cuff of his dress shirt up to the elbow and held out his forearm for me to gaze upon.

I looked.

Then I stood dumbfounded, for half-way up the forearm, on the inside, was the cicatrice of an old knife wound which long ago, he had told me, had been made by an Indian in South America who had attempted to kill him, and whom he had shot in self-defence.

"You believe me now?" he asked, in a voice scarce above a whisper.

"Of course," I said. "Pardon me, Digby—but this change in your personality is marvellous—almost superhuman!"

"So I've been told before," he replied lightly.

"But, really, didn't you penetrate it?" he asked, resuming his normal voice.

"No. I certainly did not," I answered, and helping myself to a drink, swallowed it.

"Well?" I went on. "What does this mean?"

"At present I can't exactly tell you what I intend doing," he replied. "To-night I wanted to test you, and have done so. It's late now," he added, glancing at the clock, which showed it to be half-past two o'clock in the morning. "Come in to-morrow at ten, will you?" he asked. "I want to discuss the future with you very seriously. I have something to say which concerns your own future, and which also closely concerns a friend of yours. So come in your own interests, Royle—now don't fail, I beg of you!"

"But can't you tell me to-night," I asked.

"Not until I know something of what my own movements are to be," he replied. "I cannot know before to-morrow," he replied with a mysterious air. "So if you wish to be forewarned of an impending peril, come and see me and I will then explain. We shall, no doubt, be on closer terms to-morrow. Au revoir," and he took my hand warmly and then let me out.

The rather narrow, ill-lit staircase, the outer door of which had been shut for hours, was close and stuffy, but as I descended the second flight and was about to pass along the hall to the door, I distinctly heard a movement in the shadow where, on my left, the hall continued along to the door of the ground-floor flat.

I peered over the banisters, but in the darkness could distinguish nothing.

That somebody was lurking there I instantly felt assured, and next moment the truth became revealed by two facts.

The first was a light, almost imperceptible noise, the jingle of a woman's bangles, and, secondly, the faint odour of some subtle perfume, a sweet, intoxicating scent such as my nostrils had never greeted before.

For the moment I felt surprise, but as the hidden lady was apparently standing outside the ground-floor flat—perhaps awaiting admittance—I felt it to be no concern of mine, and proceeding, opened the outer door and passed outside, closing it quietly after me.

An unusually sweet perfume one can seldom forget. Even out in the keen night air that delightful odour seemed to cling to my memory—the latest creation of the Rue de la Paix, I supposed.

Well, I duly returned home to Albemarle Street once again, utterly mystified.

What did it all mean? Why had Digby adopted such a marvellous disguise? What did he mean by saying that he wished to stand my friend and safeguard me from impending evil?

Yes, it was all a mystery—but surely not so great a mystery as that which was to follow. Ah! had I but suspected the astounding truth how very differently would I have acted!

Filled with curiosity regarding Digby's strange forebodings, I alighted from a taxi in Harrington Gardens at a quarter to eleven that same morning, but on entering found the uniformed hall-porter in a great state of excitement and alarm.

"Oh, sir!" he cried breathlessly, advancing towards me. "You're a friend of Sir Digby's sir. The police are upstairs. Something extraordinary has happened."

"The police!" I gasped. "Why, what's happened?"

"Well, sir. As his man left the day before yesterday, my wife went up to Sir Digby's flat as usual this morning about eight, and put him his early cup of tea outside his door. But when she went in again she found he had not taken it into his room. She believed him to be asleep, so not till ten o'clock did she go into the sitting-room to draw up the blinds, when, to her horror, she found a young lady, a perfect stranger, lying stretched on the floor there! She rushed down and told me, and I went up. I found that Sir Digby's bed hadn't been slept in, and that though the poor girl was unconscious, she was still breathing. So I at once called in the constable on point duty at the corner of Collingham Road, and he 'phoned to the police station."

"But the girl—is she dead?" I inquired quickly.

"I don't know, sir. You'd better go upstairs. There's an inspector, two plain-clothes men, and a doctor up there."

He took me up in the lift, and a few moments later I stood beside Digby's bed, whereon the men had laid the inanimate form of a well-dressed girl whom I judged to be about twenty-two, whose dark hair, unbound, lay in disorder upon the pillow. The face, white as marble, was handsome and clean cut, but upon it, alas! was the ashen hue of death, the pale lips slightly parted as though in a half-sarcastic smile.

The doctor was bending over her making his examination.

I looked upon her for a moment, but it was a countenance which I had never seen before. Digby had many lady friends, but I had never seen her among them. She was a perfect stranger.

Her gown was of dark blue serge, smartly made, and beneath her coat she wore a cream silk blouse with deep sailor collar open at the neck, and a soft flowing bow of turquoise blue. This, however, had been disarranged by the doctor in opening her blouse to listen to her breathing, and I saw that upon it was a small crimson stain.

Yes, she was remarkably good-looking, without a doubt.

When I announced myself as an intimate friend of Sir Digby Kemsley, the inspector at once took me into the adjoining room and began to eagerly question me.

With him I was perfectly frank; but I said nothing regarding my second visit there in the night.

My gravest concern was the whereabouts of my friend.

"This is a very curious case, Mr. Royle," declared the inspector. "The C.I.D. men have established one fact—that another woman was with the stranger here in the early hours of this morning. This hair-comb"—and he showed me a small side-comb of dark green horn—"was found close beside her on the floor. Also a couple of hair-pins, which are different to those in the dead woman's hair. There was a struggle, no doubt, and the woman got away. In the poor girl's hair are two tortoiseshell side-combs."

"But what is her injury?" I asked breathlessly.

"She's been stabbed," he replied. "Let's go back."

Together we re-entered the room, but as we did so we saw that the doctor had now left the bedside, and was speaking earnestly with the two detectives.

"Well, doctor?" asked the inspector in a low voice.

"She's quite dead—murder, without a doubt," was his reply. "The girl was struck beneath the left breast—a small punctured wound, but fatal!"

"The woman who left this hair-comb behind knows something about the affair evidently," exclaimed the inspector. "We must first discover Sir Digby Kemsley. He seems to have been here up until eleven o'clock last night. Then he mysteriously disappeared, and the stranger entered unseen, two very curious and suspicious circumstances. I wonder who the poor girl was?"

The two detectives were discussing the affair in low voices. Here was a complete and very remarkable mystery, which, from the first, the police told me they intended to keep to themselves, and not allow a syllable of it to leak out to the public through the newspapers.

A woman had been there!

Did there not exist vividly in my recollection that strange encounter in the darkness of the stairs? The jingle of the golden bangles, and the sweet odour of that delicious perfume?

But I said nothing. I intended that the police should prosecute their inquiries, find my friend, and establish the identity of the mysterious girl who had met with such an untimely end presumably at the hands of that woman who had been lurking in the darkness awaiting my departure.

Truly it was a mystery, a most remarkable problem among the many which occur each week amid the amazing labyrinth of humanity which we term London life.

Sir Digby Kemsley had disappeared. Where?

Half an hour after noon I had left Harrington Gardens utterly bewildered, and returned to Albemarle Street, and at half-past one met Phrida at the Berkeley, where, as I have already described, we lunched together.

I had revealed to her everything under seal of the secrecy placed upon me by the police—everything save that suspicion I had had in the darkness, and the suspicion the police also held—the suspicion of a woman.

Relation of the curious affair seemed to have unnerved her. She had become paler and was fidgeting with her serviette. Loving me so devotedly, she seemed to entertain vague and ridiculous fears regarding my own personal safety.

"It was very foolish and hazardous of you to have returned there at that hour, dear," she declared with sweet solicitation, as she drew on her white gloves preparatory to leaving the restaurant, for I had already paid the bill and drained my liqueur-glass.

"I don't see why," I said. "Whatever could have happened to me, when——"

My sentence remained unfinished.

I held my breath. The colour must have left my cheeks, I know.

My well-beloved had at that moment opened her handbag and taken out her wisp of lace handkerchief.

My nostrils were instantly filled with that same sweet, subtle perfume which I so vividly recollected, the identical perfume of the woman concealed in that dark passage-way!

Her bangles, two thin gold ones, jingled as she moved—that same sound which had come up to me from the blackness. I sat like a statue, staring at her amazed, aghast, like a man in a dream.