"A GENTLEMAN to see you, Doctor."

　　From across the common a clock sounded the half-hour.

　　"Ten-thirty!" I said. "A late visitor. Show him up, if you please."

　　I pushed my writing aside and tilted the lamp-shade, as footstepssounded on the landing. The next moment I had jumped to my feet, for atall, lean man, with his square-cut, clean-shaven face sun-baked to thehue of coffee, entered and extended both hands, with a cry:

　　"Good old Petrie! Didn't expect me, I'll swear!"

　　It was Nayland Smith--whom I had thought to be in Burma!

　　"Smith," I said, and gripped his hands hard, "this is a delightfulsurprise! Whatever--however--"

　　"Excuse me, Petrie!" he broke in. "Don't put it down to the sun!" Andhe put out the lamp, plunging the room into darkness.

　　I was too surprised to speak.

　　"No doubt you will think me mad," he continued, and, dimly, I could seehim at the window, peering out into the road, "but before you are manyhours older you will know that I have good reason to be cautious. Ah,nothing suspicious! Perhaps I am first this time." And, stepping backto the writing-table he relighted the lamp.

　　"Mysterious enough for you?" he laughed, and glanced at my unfinishedMS. "A story, eh? From which I gather that the district is beastlyhealthy--what, Petrie? Well, I can put some material in your way that,if sheer uncanny mystery is a marketable commodity, ought to make youindependent of influenza and broken legs and shattered nerves and allthe rest."

　　I surveyed him doubtfully, but there was nothing in his appearance tojustify me in supposing him to suffer from delusions. His eyes weretoo bright, certainly, and a hardness now had crept over his face. Igot out the whisky and siphon, saying:

　　"You have taken your leave early?"

　　"I am not on leave," he replied, and slowly filled his pipe. "I am onduty."

　　"On duty!" I exclaimed. "What, are you moved to London or something?"

　　"I have got a roving commission, Petrie, and it doesn't rest with mewhere I am to-day nor where I shall be to-morrow."

　　There was something ominous in the words, and, putting down my glass,its contents untasted, I faced round and looked him squarely in theeyes. "Out with it!" I said. "What is it all about?"

　　Smith suddenly stood up and stripped off his coat. Rolling back hisleft shirt-sleeve he revealed a wicked-looking wound in the fleshy partof the forearm. It was quite healed, but curiously striated for aninch or so around.

　　"Ever seen one like it?" he asked.

　　"Not exactly," I confessed. "It appears to have been deeplycauterized."

　　"Right! Very deeply!" he rapped. "A barb steeped in the venom of ahamadryad went in there!"

　　A shudder I could not repress ran coldly through me at mention of thatmost deadly of all the reptiles of the East.

　　"There's only one treatment," he continued, rolling his sleeve downagain, "and that's with a sharp knife, a match, and a broken cartridge.I lay on my back, raving, for three days afterwards, in a forest thatstank with malaria, but I should have been lying there now if I hadhesitated. Here's the point. It was not an accident!"

　　"What do you mean?"

　　"I mean that it was a deliberate attempt on my life, and I am hard uponthe tracks of the man who extracted that venom--patiently, drop bydrop--from the poison-glands of the snake, who prepared that arrow, andwho caused it to be shot at me."

　　"What fiend is this?"

　　"A fiend who, unless my calculations are at fault is now in London, andwho regularly wars with pleasant weapons of that kind. Petrie, I havetraveled from Burma not in the interests of the British Governmentmerely, but in the interests of the entire white race, and I honestlybelieve--though I pray I may be wrong--that its survival dependslargely upon the success of my mission."

　　To say that I was perplexed conveys no idea of the mental chaos createdby these extraordinary statements, for into my humdrum suburban lifeNayland Smith had brought fantasy of the wildest. I did not know whatto think, what to believe.

　　"I am wasting precious time!" he rapped decisively, and, draining hisglass, he stood up. "I came straight to you, because you are the onlyman I dare to trust. Except the big chief at headquarters, you are theonly person in England, I hope, who knows that Nayland Smith hasquitted Burma. I must have someone with me, Petrie, all the time--it'simperative! Can you put me up here, and spare a few days to thestrangest business, I promise you, that ever was recorded in fact orfiction?"

　　I agreed readily enough, for, unfortunately, my professional dutieswere not onerous.

　　"Good man!" he cried, wringing my hand in his impetuous way. "We startnow."

　　"What, to-night?"

　　"To-night! I had thought of turning in, I must admit. I have notdared to sleep for forty-eight hours, except in fifteen-minutestretches. But there is one move that must be made to-night andimmediately. I must warn Sir Crichton Davey."

　　"Sir Crichton Davey--of the India--"

　　"Petrie, he is a doomed man! Unless he follows my instructions withoutquestion, without hesitation--before Heaven, nothing can save him! Ido not know when the blow will fall, how it will fall, nor from whence,but I know that my first duty is to warn him. Let us walk down to thecorner of the common and get a taxi."

　　How strangely does the adventurous intrude upon the humdrum; for, whenit intrudes at all, more often than not its intrusion is sudden andunlooked for. To-day, we may seek for romance and fail to find it:unsought, it lies in wait for us at most prosaic corners of life'shighway.

　　The drive that night, though it divided the drably commonplace from thewildly bizarre--though it was the bridge between the ordinary and theoutre--has left no impression upon my mind. Into the heart of a weirdmystery the cab bore me; and in reviewing my memories of those days Iwonder that the busy thoroughfares through which we passed did notdisplay before my eyes signs and portents--warnings.

　　It was not so. I recall nothing of the route and little of import thatpassed between us

we both were strangely silent, I think

until wewere come to our journey's end. Then:

　　"What's this?" muttered my friend hoarsely.

　　Constables were moving on a little crowd of curious idlers who pressedabout the steps of Sir Crichton Davey's house and sought to peer in atthe open door. Without waiting for the cab to draw up to the curb,Nayland Smith recklessly leaped out and I followed close at his heels.

　　"What has happened?" he demanded breathlessly of a constable.

　　The latter glanced at him doubtfully, but something in his voice andbearing commanded respect.

　　"Sir Crichton Davey has been killed, sir."

　　Smith lurched back as though he had received a physical blow, andclutched my shoulder convulsively. Beneath the heavy tan his face hadblanched, and his eyes were set in a stare of horror.

　　"My God!" he whispered. "I am too late!"

　　With clenched fists he turned and, pressing through the group ofloungers, bounded up the steps. In the hall a man who unmistakably wasa Scotland Yard official stood talking to a footman. Other members ofthe household were moving about, more or less aimlessly, and the chillyhand of King Fear had touched one and all, for, as they came and went,they glanced ever over their shoulders, as if each shadow cloaked amenace, and listened, as it seemed, for some sound which they dreadedto hear. Smith strode up to the detective and showed him a card, uponglancing at which the Scotland Yard man said something in a low voice,and, nodding, touched his hat to Smith in a respectful manner.

　　A few brief questions and answers, and, in gloomy silence, we followedthe detective up the heavily carpeted stair, along a corridor linedwith pictures and busts, and into a large library. A group of peoplewere in this room, and one, in whom I recognized Chalmers Cleeve, ofHarley Street, was bending over a motionless form stretched upon acouch. Another door communicated with a small study, and through theopening I could see a man on all fours examining the carpet. Theuncomfortable sense of hush, the group about the physician, the bizarrefigure crawling, beetle-like, across the inner room, and the grim hub,around which all this ominous activity turned, made up a scene thatetched itself indelibly on my mind.

　　As we entered Dr. Cleeve straightened himself, frowning thoughtfully.

　　"Frankly, I do not care to venture any opinion at present regarding theimmediate cause of death," he said. "Sir Crichton was addicted tococaine, but there are indications which are not in accordance withcocaine-poisoning. I fear that only a post-mortem can establish thefacts--if," he added, "we ever arrive at them. A most mysterious case!"

　　Smith stepping forward and engaging the famous pathologist inconversation, I seized the opportunity to examine Sir Crichton's body.

　　The dead man was in evening dress, but wore an old smoking-jacket. Hehad been of spare but hardy build, with thin, aquiline features, whichnow were oddly puffy, as were his clenched hands. I pushed back hissleeve, and saw the marks of the hypodermic syringe upon his left arm.Quite mechanically I turned my attention to the right arm. It wasunscarred, but on the back of the hand was a faint red mark, not unlikethe imprint of painted lips. I examined it closely, and even tried torub it off, but it evidently was caused by some morbid process of localinflammation, if it were not a birthmark.

　　Turning to a pale young man whom I had understood to be Sir Crichton'sprivate secretary, I drew his attention to this mark, and inquired ifit were constitutional. "It is not, sir," answered Dr. Cleeve,overhearing my question. "I have already made that inquiry. Does itsuggest anything to your mind? I must confess that it affords me noassistance."

　　"Nothing," I replied. "It is most curious."

　　"Excuse me, Mr. Burboyne," said Smith, now turning to the secretary,"but Inspector Weymouth will tell you that I act with authority. Iunderstand that Sir Crichton was--seized with illness in his study?"

　　"Yes--at half-past ten. I was working here in the library, and heinside, as was our custom."

　　"The communicating door was kept closed?"

　　"Yes, always. It was open for a minute or less about ten-twenty-five,when a message came for Sir Crichton. I took it in to him, and he thenseemed in his usual health."

　　"What was the message?"

　　"I could not say. It was brought by a district messenger, and heplaced it beside him on the table. It is there now, no doubt."

　　"And at half-past ten?"

　　"Sir Crichton suddenly burst open the door and threw himself, with ascream, into the library. I ran to him but he waved me back. His eyeswere glaring horribly. I had just reached his side when he fell,writhing, upon the floor. He seemed past speech, but as I raised himand laid him upon the couch, he gasped something that sounded like 'Thered hand!' Before I could get to bell or telephone he was dead!"

　　Mr. Burboyne's voice shook as he spoke the words, and Smith seemed tofind this evidence confusing.

　　"You do not think he referred to the mark on his own hand?"

　　"I think not. From the direction of his last glance, I feel sure hereferred to something in the study."

　　"What did you do?"

　　"Having summoned the servants, I ran into the study. But there wasabsolutely nothing unusual to be seen. The windows were closed andfastened. He worked with closed windows in the hottest weather. Thereis no other door, for the study occupies the end of a narrow wing, sothat no one could possibly have gained access to it, whilst I was inthe library, unseen by me. Had someone concealed himself in the studyearlier in the evening--and I am convinced that it offers nohiding-place--he could only have come out again by passing throughhere."

　　Nayland Smith tugged at the lobe of his left ear, as was his habit whenmeditating.

　　"You had been at work here in this way for some time?"

　　"Yes. Sir Crichton was preparing an important book."

　　"Had anything unusual occurred prior to this evening?"

　　"Yes," said Mr. Burboyne, with evident perplexity; "though I attachedno importance to it at the time. Three nights ago Sir Crichton cameout to me, and appeared very nervous; but at times his nerves--youknow? Well, on this occasion he asked me to search the study. He hadan idea that something was concealed there."

　　"Some THING or someone?"

　　"'Something' was the word he used. I searched, but fruitlessly, and heseemed quite satisfied, and returned to his work."

　　"Thank you, Mr. Burboyne. My friend and I would like a few minutes'private investigation in the study."