i was making experiments of some interest at south kensington, and hoped that i had perfected a small but not unimportant discovery, when, on returning home one evening in late october in the year 1893, i found a visiting card on my table. on it were inscribed the words, "mr. geoffrey bainbridge." this name was quite unknown to me, so i rang the bell and inquired of my servant who the visitor had been. he described him as a gentleman who wished to see me on most urgent business, and said further that mr. bainbridge intended to call again later in the

evening. it was with both curiosity and vexation that i awaited the return of the stranger. urgent business with me generally meant a hurried rush to one part of the country or the other. i did not want to leave london just then; and when at half-past nine mr. geoffrey bainbridge was ushered into my room, i received him with a certain coldness which he could not fail to perceive. he was a tall, well-dressed, elderly man. he immediately plunged into the object of his visit.

"i hope you do not consider my unexpected presence an intrusion, mr. bell," he said. "but i have heard of you from our mutual friends, the greys of uplands. you may remember once doing that family a great service."

"i remember perfectly well," i answered more cordially. "pray tell me what you want; i shall listen with attention."

"i believe you are the one man in london who can help me," he continued. "i refer to a matter especially relating to your own particular study. i need hardly say

that whatever you do will not be unrewarded."

"that is neither here nor there," i said; "but before you go any further, allow me to ask one question. do you want me to leave london at present?"

he raised his eyebrows in dismay.

"i certainly do," he answered.

"very well; pray proceed with your story."

he looked at me with anxiety.

"in the first place," he began, "i must tell you that i am chairman of the lytton vale railway company in wales, and that it is on an important matter connected with our line that i have come to consult you. when i explain to you the nature of the mystery, you will not wonder, i think, at my soliciting your aid."

"i will give you my closest attention," i answered; and then i added, impelled to say the latter words by a certain expression on his face, "if i can see my way to assisting you i shall be ready to do so."

"pray accept my cordial thanks," he

replied. "i have come up from my place at felwyn to-day on purpose to consult you. it is in that neighbourhood that the affair has occurred. as it is essential that you should be in possession of the facts of the whole matter, i will go over things just as they happened."

i bent forward and listened attentively.

"this day fortnight," continued mr. bainbridge, "our quiet little village was horrified by the news that the signalman on duty at the mouth of the felwyn tunnel had been found dead under the most mysterious circumstances. the tunnel is at the end of a long cutting between llanlys and felwyn stations. it is about a mile long, and the signal-box is on the felwyn side. the place is extremely lonely, being six miles from the village across the mountains. the name of the poor fellow who met his death in this mysterious fashion was david pritchard. i have known him from a boy, and he was quite one of the steadiest and most trustworthy men on the line. on tuesday evening he went on duty at six

o'clock; on wednesday morning the day-man who had come to relieve him was surprised not to find him in the box. it was just getting daylight, and the 6.30 local was coming down, so he pulled the signals and let her through. then he went out, and, looking up the line towards the tunnel, saw pritchard lying beside the line close to the mouth of the tunnel. roberts, the day-man, ran up to him and found, to his horror, that he was quite dead. at first roberts naturally supposed that he had been cut down by a train, as there was a wound at the back of the head; but he was not lying on the metals. roberts ran back to the box and telegraphed through to felwyn station. the message was sent on to the village, and at half-past seven o'clock the police inspector came up to my house with the news. he and i, with the local doctor, went off at once to the tunnel. we found the dead man lying beside the metals a few yards away from the mouth of the tunnel, and the doctor immediately gave him a careful examination. there was a depressed

fracture at the back of the skull, which must have caused his death; but how he came by it was not so clear. on examining the whole place most carefully, we saw, further, that there were marks on the rocks at the steep side of the embankment as if some one had tried to scramble up them. why the poor fellow had attempted such a climb, god only knows. in doing so he must have slipped and fallen back on to the line, thus causing the fracture of the skull. in no case could he have gone up more than eight or ten feet, as the banks of the cutting run sheer up, almost perpendicularly, beyond that point for more than a hundred and fifty feet. there are some sharp boulders beside the line, and it was possible that he might have fallen on one of these and so sustained the injury. the affair must have occurred some time between 11.45 p.m. and 6 a.m., as the engine-driver of the express at 11.45 p.m. states that the line was signalled clear, and he also caught sight of pritchard in his box as he passed."

"this is deeply interesting," i said; "pray proceed."

bainbridge looked at me earnestly; he then continued:—

"the whole thing is shrouded in mystery. why should pritchard have left his box and gone down to the tunnel? why, having done so, should he have made a wild attempt to scale the side of the cutting, an impossible feat at any time? had danger threatened, the ordinary course of things would have been to run up the line towards the signal-box. these points are quite unexplained. another curious fact is that death appears to have taken place just before the day-man came on duty, as the light at the mouth of the tunnel had been put out, and it was one of the night signalman's duties to do this as soon as daylight appeared; it is possible, therefore, that pritchard went down to the tunnel for that purpose. against this theory, however, and an objection that seems to nullify it, is the evidence of dr. williams, who states that when he examined the body his opinion was

that death had taken place some hours before. an inquest was held on the following day, but before it took place there was a new and most important development. i now come to what i consider the crucial point in the whole story.

"for a long time there had been a feud between pritchard and another man of the name of wynne, a platelayer on the line. the object of their quarrel was the blacksmith's daughter in the neighbouring village—a remarkably pretty girl and an arrant flirt. both men were madly in love with her, and she played them off one against the other. the night but one before his death pritchard and wynne had met at the village inn, had quarrelled in the bar—lucy, of course, being the subject of their difference. wynne was heard to say (he was a man of powerful build and subject to fits of ungovernable rage) that he would have pritchard's life. pritchard swore a great oath that he would get lucy on the following day to promise to marry him. this oath, it appears, he kept, and on his

way to the signal-box on tuesday evening met wynne, and triumphantly told him that lucy had promised to be his wife. the men had a hand-to-hand fight on the spot, several people from the village being witnesses of it. they were separated with difficulty, each vowing vengeance on the other. pritchard went off to his duty at the signal-box and wynne returned to the village to drown his sorrows at the public-house.

"very late that same night wynne was seen by a villager going in the direction of the tunnel. the man stopped him and questioned him. he explained that he had left some of his tools on the line, and was on his way to fetch them. the villager noticed that he looked queer and excited, but not wishing to pick a quarrel thought it best not to question him further. it has been proved that wynne never returned home that night, but came back at an early hour on the following morning, looking dazed and stupid. he was arrested on suspicion, and at the inquest the verdict was against him."

"has he given any explanation of his own movements?" i asked.

"yes; but nothing that can clear him. as a matter of fact, his tools were nowhere to be seen on the line, nor did he bring them home with him. his own story is that being considerably the worse for drink, he had fallen down in one of the fields and slept there till morning."

"things look black against him," i said.

"they do; but listen, i have something more to add. here comes a very queer feature in the affair. lucy ray, the girl who had caused the feud between pritchard and wynne, after hearing the news of pritchard's death, completely lost her head, and ran frantically about the village declaring that wynne was the man she really loved, and that she had only accepted pritchard in a fit of rage with wynne for not himself bringing matters to the point. the case looks very bad against wynne, and yesterday the magistrate committed him for trial at the coming assizes. the unhappy lucy ray and the young

man's parents are in a state bordering on distraction."

"what is your own opinion with regard to wynne's guilt?" i asked.

"before god, mr. bell, i believe the poor fellow is innocent, but the evidence against him is very strong. one of the favourite theories is that he went down to the tunnel and extinguished the light, knowing that this would bring pritchard out of his box to see what was the matter, and that he then attacked him, striking the blow which fractured the skull."

"has any weapon been found about, with which he could have given such a blow?"

"no; nor has anything of the kind been discovered on wynne's person; that fact is decidedly in his favour."

"but what about the marks on the rocks?" i asked.

"it is possible that wynne may have made them in order to divert suspicion by making people think that pritchard must have fallen, and so killed himself. the holders of this theory base their belief on the absolute want

of cause for pritchard's trying to scale the rock. the whole thing is the most absolute enigma. some of the country folk have declared that the tunnel is haunted (and there certainly has been such a rumour current among them for years). that pritchard saw some apparition, and in wild terror sought to escape from it by climbing the rocks, is another theory, but only the most imaginative hold it."

"well, it is a most extraordinary case," i replied.

"yes, mr. bell, and i should like to get your opinion of it. do you see your way to elucidate the mystery?"

"not at present; but i shall be happy to investigate the matter to my utmost ability."

"but you do not wish to leave london at present?"

"that is so; but a matter of such importance cannot be set aside. it appears, from what you say, that wynne's life hangs more or less on my being able to clear away the mystery?"

"that is indeed the case. there ought not to be a single stone left unturned to get at the truth, for the sake of wynne. well, mr. bell, what do you propose to do?"

"to see the place without delay," i answered.

"that is right; when can you come?"

"whenever you please."

"will you come down to felwyn with me to-morrow? i shall leave paddington by the 7.10, and if you will be my guest i shall be only too pleased to put you up."

"that arrangement will suit me admirably," i replied. "i will meet you by the train you mention, and the affair shall have my best attention."

"thank you," he said, rising. he shook hands with me and took his leave.

the next day i met bainbridge at paddington station, and we were soon flying westward in the luxurious private compartment that had been reserved for him. i could see by his abstracted manner and his long lapses of silence that the mysterious affair

at felwyn tunnel was occupying all his thoughts.

it was two o'clock in the afternoon when the train slowed down at the little station of felwyn. the station-master was at the door in an instant to receive us.

"i have some terribly bad news for you, sir," he said, turning to bainbridge as we alighted; "and yet in one sense it is a relief, for it seems to clear wynne."

"what do you mean?" cried bainbridge. "bad news? speak out at once!"

"well, sir, it is this: there has been another death at felwyn signal-box. john davidson, who was on duty last night, was found dead at an early hour this morning in the very same place where we found poor pritchard."

"good god!" cried bainbridge, starting back, "what an awful thing! what, in the name of heaven, does it mean, mr. bell? this is too fearful. thank goodness you have come down with us."

"it is as black a business as i ever heard of, sir," echoed the station-master; "and what

we are to do i don't know. poor davidson was found dead this morning, and there was neither mark nor sign of what killed him—that is the extraordinary part of it. there's a perfect panic abroad, and not a signalman on the line will take duty to-night. i was quite in despair, and was afraid at one time that the line would have to be closed, but at last it occurred to me to wire to lytton vale, and they are sending down an inspector. i expect him by a special every moment. i believe this is he coming now," added the station-master, looking up the line.

there was the sound of a whistle down the valley, and in a few moments a single engine shot into the station, and an official in uniform stepped on to the platform.

"good-evening, sir," he said, touching his cap to bainbridge; "i have just been sent down to inquire into this affair at the felwyn tunnel, and though it seems more of a matter for a scotland yard detective than one of ourselves, there was nothing for it but to come. all the same, mr. bainbridge, i cannot

say that i look forward to spending to-night alone at the place."

"you wish for the services of a detective, but you shall have some one better," said bainbridge, turning towards me. "this gentleman, mr. john bell, is the man of all others for our business. i have just brought him down from london for the purpose."

an expression of relief flitted across the inspector's face.

"i am very glad to see you, sir," he said to me, "and i hope you will be able to spend the night with me in the signal-box. i must say i don't much relish the idea of tackling the thing single-handed; but with your help, sir, i think we ought to get to the bottom of it somehow. i am afraid there is not a man on the line who will take duty until we do. so it is most important that the thing should be cleared, and without delay."

i readily assented to the inspector's proposition, and bainbridge and i arranged that we should call for him at four o'clock at the village inn and drive him to the tunnel.

we then stepped into the wagonette

which was waiting for us, and drove to bainbridge's house.

mrs. bainbridge came out to meet us, and was full of the tragedy. two pretty girls also ran to greet their father, and to glance inquisitively at me. i could see that the entire family was in a state of much excitement.

"lucy ray has just left, father," said the elder of the girls. "we had much trouble to soothe her; she is in a frantic state."

"you have heard, mr. bell, all about this dreadful mystery?" said mrs. bainbridge as she led me towards the dining-room.

"yes," i answered; "your husband has been good enough to give me every particular."

"and you have really come here to help us?"

"i hope i may be able to discover the cause," i answered.

"it certainly seems most extraordinary," continued mrs. bainbridge. "my dear," she continued, turning to her husband, "you can easily imagine the state we were all in this

morning when the news of the second death was brought to us."

"for my part," said ella bainbridge, "i am sure that felwyn tunnel is haunted. the villagers have thought so for a long time, and this second death seems to prove it, does it not?" here she looked anxiously at me.

"i can offer no opinion," i replied, "until i have sifted the matter thoroughly."

"come, ella, don't worry mr. bell," said her father; "if he is as hungry as i am, he must want his lunch."

we then seated ourselves at the table and commenced the meal. bainbridge, although he professed to be hungry, was in such a state of excitement that he could scarcely eat. immediately after lunch he left me to the care of his family and went into the village.

"it is just like him," said mrs. bainbridge; "he takes these sort of things to heart dreadfully. he is terribly upset about lucy ray, and also about the poor fellow wynne. it is certainly a fearful tragedy from first to last."

"well, at any rate," i said, "this fresh death will upset the evidence against wynne."

"i hope so, and there is some satisfaction in the fact. well, mr. bell, i see you have finished lunch; will you come into the drawing-room?"

i followed her into a pleasant room overlooking the valley of the lytton.

by-and-by bainbridge returned, and soon afterwards the dog-cart came to the door. my host and i mounted, bainbridge took the reins, and we started off at a brisk pace.

"matters get worse and worse," he said the moment we were alone. "if you don't clear things up to-night, bell, i say frankly that i cannot imagine what will happen."

we entered the village, and as we rattled down the ill-paved streets i was greeted with curious glances on all sides. the people were standing about in groups, evidently talking about the tragedy and nothing else. suddenly, as our trap bumped noisily over the paving-stones, a girl darted out of one of

the houses and made frantic motions to bainbridge to stop the horse. he pulled the mare nearly up on her haunches, and the girl came up to the side of the dog-cart.

"you have heard it?" she said, speaking eagerly and in a gasping voice. "the death which occurred this morning will clear stephen wynne, won't it, mr. bainbridge?—it will, you are sure, are you not?"

"it looks like it, lucy, my poor girl," he answered. "but there, the whole thing is so terrible that i scarcely know what to think."

she was a pretty girl with dark eyes, and under ordinary circumstances must have had the vivacious expression of face and the brilliant complexion which so many of her countrywomen possess. but now her eyes were swollen with weeping and her complexion more or less disfigured by the agony she had gone through. she looked piteously at bainbridge, her lips trembling. the next moment she burst into tears.

"come away, lucy," said a woman who had followed her out of the cottage; "fie—for

shame! don't trouble the gentlemen; come back and stay quiet."

"i can't, mother, i can't," said the unfortunate girl. "if they hang him, i'll go clean off my head. oh, mr. bainbridge, do say that the second death has cleared him!"

"i have every hope that it will do so, lucy," said bainbridge, "but now don't keep us, there's a good girl; go back into the house. this gentleman has come down from london on purpose to look into the whole matter. i may have good news for you in the morning."

the girl raised her eyes to my face with a look of intense pleading. "oh, i have been cruel and a fool, and i deserve everything," she gasped; "but, sir, for the love of heaven, try to clear him."

i promised to do my best.

bainbridge touched up the mare, she bounded forward, and lucy disappeared into the cottage with her mother.

the next moment we drew up at the inn where the inspector was waiting, and soon afterwards were bowling along between the

high banks of the country lanes to the tunnel. it was a cold, still afternoon; the air was wonderfully keen, for a sharp frost had held the countryside in its grip for the last two days. the sun was just tipping the hills to westward when the trap pulled up at the top of the cutting. we hastily alighted, and the inspector and i bade bainbridge good-bye. he said that he only wished that he could stay with us for the night, assured us that little sleep would visit him, and that he would be back at the cutting at an early hour on the following morning; then the noise of his horse's feet was heard fainter and fainter as he drove back over the frost-bound roads. the inspector and i ran along the little path to the wicket-gate in the fence, stamping our feet on the hard ground to restore circulation after our cold drive. the next moment we were looking down upon the scene of the mysterious deaths, and a weird and lonely place it looked. the tunnel was at one end of the rock cutting, the sides of which ran sheer down to the line for over a hundred and fifty feet. above the tunnel's

mouth the hills rose one upon the other. a more dreary place it would have been difficult to imagine. from a little clump of pines a delicate film of blue smoke rose straight up on the still air. this came from the chimney of the signal-box.

as we started to descend the precipitous path the inspector sang out a cheery "hullo!" the man on duty in the box immediately answered. his voice echoed and reverberated down the cutting, and the next moment he appeared at the door of the box. he told us that he would be with us immediately; but we called back to him to stay where he was, and the next instant the inspector and i entered the box.

"the first thing to do," said henderson the inspector, "is to send a message down the line to announce our arrival."

this he did, and in a few moments a crawling goods train came panting up the cutting. after signalling her through we descended the wooden flight of steps which led from the box down to the line and walked along the metals towards the tunnel

till we stood on the spot where poor davidson had been found dead that morning. i examined the ground and all around it most carefully. everything tallied exactly with the description i had received. there could be no possible way of approaching the spot except by going along the line, as the rocky sides of the cutting were inaccessible.

"it is a most extraordinary thing, sir," said the signalman whom we had come to relieve. "davidson had neither mark nor sign on him—there he lay stone dead and cold, and not a bruise nowhere; but pritchard had an awful wound at the back of the head. they said he got it by climbing the rocks—here, you can see the marks for yourself, sir. but now, is it likely that pritchard would try to climb rocks like these, so steep as they are?"

"certainly not," i replied.

"then how do you account for the wound, sir?" asked the man with an anxious face.

"i cannot tell you at present," i answered.

"and you and inspector henderson are going to spend the night in the signal-box?"

"yes."

a horrified expression crept over the signalman's face.

"god preserve you both," he said; "i wouldn't do it—not for fifty pounds. it's not the first time i have heard tell that felwyn tunnel is haunted. but, there, i won't say any more about that. it's a black business, and has given trouble enough. there's poor wynne, the same thing as convicted of the murder of pritchard; but now they say that davidson's death will clear him. davidson was as good a fellow as you would come across this side of the country; but for the matter of that, so was pritchard. the whole thing is terrible—it upsets one, that it do, sir."

"i don't wonder at your feelings," i answered; "but now, see here, i want to make a most careful examination of everything. one of the theories is that wynne crept down this rocky side and fractured

pritchard's skull. i believe such a feat to be impossible. on examining these rocks i see that a man might climb up the side of the tunnel as far as from eight to ten feet, utilising the sharp projections of rock for the purpose; but it would be out of the question for any man to come down the cutting. no; the only way wynne could have approached pritchard was by the line itself. but, after all, the real thing to discover is this," i continued: "what killed davidson? whatever caused his death is, beyond doubt, equally responsible for pritchard's. i am now going into the tunnel."

inspector henderson went in with me. the place struck damp and chill. the walls were covered with green, evil-smelling fungi, and through the brickwork the moisture was oozing and had trickled down in long lines to the ground. before us was nothing but dense darkness.

when we re-appeared the signalman was lighting the red lamp on the post, which stood about five feet from the ground just above the entrance to the tunnel.

"is there plenty of oil?" asked the inspector.

"yes, sir, plenty," replied the man. "is there anything more i can do for either of you gentlemen?" he asked, pausing, and evidently dying to be off.

"nothing," answered henderson; "i will wish you good-evening."

"good-evening to you both," said the man. he made his way quickly up the path and was soon lost to sight.

henderson and i then returned to the signal-box.

by this time it was nearly dark.

"how many trains pass in the night?" i asked of the inspector.

"there's the 10.20 down express," he said, "it will pass here at about 10.40; then there's the 11.45 up, and then not another train till the 6.30 local to-morrow morning. we shan't have a very lively time," he added.

i approached the fire and bent over it, holding out my hands to try and get some warmth into them.

"it will take a good deal to persuade me to go down to the tunnel, whatever i may see there," said the man. "i don't think, mr. bell, i am a coward in any sense of the word, but there's something very uncanny about this place, right away from the rest of the world. i don't wonder one often hears of signalmen going mad in some of these lonely boxes. have you any theory to account for these deaths, sir?"

"none at present," i replied.

"this second death puts the idea of pritchard being murdered quite out of court," he continued.

"i am sure of it," i answered.

"and so am i, and that's one comfort," continued henderson. "that poor girl, lucy ray, although she was to be blamed for her conduct, is much to be pitied now; and as to poor wynne himself, he protests his innocence through thick and thin. he was a wild fellow, but not the sort to take the life of a fellow-creature. i saw the doctor this afternoon while i was waiting for you at the inn, mr. bell, and also the police

sergeant. they both say they do not know what davidson died of. there was not the least sign of violence on the body."

"well, i am as puzzled as the rest of you," i said. "i have one or two theories in my mind, but none of them will quite fit the situation."

the night was piercingly cold, and, although there was not a breath of wind, the keen and frosty air penetrated into the lonely signal-box. we spoke little, and both of us were doubtless absorbed by our own thoughts and speculations. as to henderson, he looked distinctly uncomfortable, and i cannot say that my own feelings were too pleasant. never had i been given a tougher problem to solve, and never had i been so utterly at my wits' end for a solution.

now and then the inspector got up and went to the telegraph instrument, which intermittently clicked away in its box. as he did so he made some casual remark and then sat down again. after the 10.40 had gone through, there followed a period of silence which seemed almost oppressive.

all at once the stillness was broken by the whirr of the electric bell, which sounded so sharply in our ears that we both started. henderson rose.

"that's the 11.45 coming," he said, and, going over to the three long levers, he pulled two of them down with a loud clang. the next moment, with a rush and a scream, the express tore down the cutting, the carriage lights streamed past in a rapid flash, the ground trembled, a few sparks from the engine whirled up into the darkness, and the train plunged into the tunnel.

"and now," said henderson, as he pushed back the levers, "not another train till daylight. my word, it is cold!"

it was intensely so. i piled some more wood on the fire and, turning up the collar of my heavy ulster, sat down at one end of the bench and leant my back against the wall. henderson did likewise; we were neither of us inclined to speak. as a rule, whenever i have any night work to do, i am never troubled with sleepiness, but on this occasion i felt unaccountably drowsy. i

soon perceived that henderson was in the same condition.

"are you sleepy?" i asked of him.

"dead with it, sir," was his answer; "but there's no fear, i won't drop off."

i got up and went to the window of the box. i felt certain that if i sat still any longer i should be in a sound sleep. this would never do. already it was becoming a matter of torture to keep my eyes open. i began to pace up and down; i opened the door of the box and went out on the little platform.

"what's the matter, sir?" inquired henderson, jumping up with a start.

"i cannot keep awake," i said.

"nor can i," he answered, "and yet i have spent nights and nights of my life in signal-boxes and never was the least bit drowsy; perhaps it's the cold."

"perhaps it is," i said; "but i have been out on as freezing nights before, and——"

the man did not reply; he had sat down again; his head was nodding.

i was just about to go up to him and

shake him, when it suddenly occurred to me that i might as well let him have his sleep out. i soon heard him snoring, and he presently fell forward in a heap on the floor. by dint of walking up and down, i managed to keep from dropping off myself, and in torture which i shall never be able to describe, the night wore itself away. at last, towards morning, i awoke henderson.

"you have had a good nap," i said; "but never mind, i have been on guard and nothing has occurred."

"good god! have i been asleep?" cried the man.

"sound," i answered.

"well, i never felt anything like it," he replied. "don't you find the air very close, sir?"

"no," i said; "it is as fresh as possible; it must be the cold."

"i'll just go and have a look at the light at the tunnel," said the man; "it will rouse me."

he went on to the little platform, whilst i bent over the fire and began to build it up.

presently he returned with a scared look on his face. i could see by the light of the oil lamp which hung on the wall that he was trembling.

"mr. bell," he said, "i believe there is somebody or something down at the mouth of the tunnel now." as he spoke he clutched me by the arm. "go and look," he said; "whoever it is, it has put out the light."

"put out the light?" i cried. "why, what's the time?"

henderson pulled out his watch.

"thank goodness, most of the night is gone," he said; "i didn't know it was so late, it is half-past five."

"then the local is not due for an hour yet?" i said.

"no; but who should put out the light?" cried henderson.

i went to the door, flung it open, and looked out. the dim outline of the tunnel was just visible looming through the darkness, but the red light was out.

"what the dickens does it mean, sir?"

gasped the inspector. "i know the lamp had plenty of oil in it. can there be any one standing in front of it, do you think?"

we waited and watched for a few moments, but nothing stirred.

"come along," i said, "let us go down together and see what it is."

"i don't believe i can do it, sir; i really don't!"

"nonsense," i cried. "i shall go down alone if you won't accompany me. just hand me my stick, will you?"

"for god's sake, be careful, mr. bell. don't go down, whatever you do. i expect this is what happened before, and the poor fellows went down to see what it was and died there. there's some devilry at work, that's my belief."

"that is as it may be," i answered shortly; "but we certainly shall not find out by stopping here. my business is to get to the bottom of this, and i am going to do it. that there is danger of some sort, i have very little doubt; but danger or not, i am going down."

"if you'll be warned by me, sir, you'll just stay quietly here."

"i must go down and see the matter out," was my answer. "now listen to me, henderson. i see that you are alarmed, and i don't wonder. just stay quietly where you are and watch, but if i call come at once. don't delay a single instant. remember i am putting my life into your hands. if i call 'come,' just come to me as quick as you can, for i may want help. give me that lantern."

he unhitched it from the wall, and taking it from him, i walked cautiously down the steps on to the line. i still felt curiously, unaccountably drowsy and heavy. i wondered at this, for the moment was such a critical one as to make almost any man wide awake. holding the lamp high above my head, i walked rapidly along the line. i hardly knew what i expected to find. cautiously along the metals i made my way, peering right and left until i was close to the fatal spot where the bodies had been found. an uncontrollable shudder

passed over me. the next moment, to my horror, without the slightest warning, the light i was carrying went out, leaving me in total darkness. i started back, and stumbling against one of the loose boulders reeled against the wall and nearly fell. what was the matter with me? i could hardly stand. i felt giddy and faint, and a horrible sensation of great tightness seized me across the chest. a loud ringing noise sounded in my ears. struggling madly for breath, and with the fear of impending death upon me, i turned and tried to run from a danger i could neither understand nor grapple with. but before i had taken two steps my legs gave way from under me, and uttering a loud cry i fell insensible to the ground.

out of an oblivion which, for all i knew, might have lasted for moments or centuries, a dawning consciousness came to me. i knew that i was lying on hard ground; that i was absolutely incapable of realising, nor had i the slightest inclination to discover,

where i was. all i wanted was to lie quite still and undisturbed. presently i opened my eyes.

some one was bending over me and looking into my face.

"thank god, he is not dead," i heard in whispered tones. then, with a flash, memory returned to me.

"what has happened?" i asked.

"you may well ask that, sir," said the inspector gravely. "it has been touch and go with you for the last quarter of an hour; and a near thing for me too."

i sat up and looked around me. daylight was just beginning to break, and i saw that we were at the bottom of the steps that led up to the signal-box. my teeth were chattering with the cold and i was shivering like a man with ague.

"i am better now," i said; "just give me your hand."

i took his arm, and holding the rail with the other hand staggered up into the box and sat down on the bench.

"yes, it has been a near shave," i said;

"and a big price to pay for solving a mystery."

"do you mean to say you know what it is?" asked henderson eagerly.

"yes," i answered, "i think i know now; but first tell me how long was i unconscious?"

"a good bit over half an hour, sir, i should think. as soon as i heard you call out i ran down as you told me, but before i got to you i nearly fainted. i never had such a horrible sensation in my life. i felt as weak as a baby, but i just managed to seize you by the arms and drag you along the line to the steps, and that was about all i could do."

"well, i owe you my life," i said; "just hand me that brandy flask, i shall be the better for some of its contents."

i took a long pull. just as i was laying the flask down henderson started from my side.

"there," he cried, "the 6.30 is coming." the electric bell at the instrument suddenly began to ring. "ought i to let her go through, sir?" he inquired.

"certainly," i answered. "that is exactly what we want. oh, she will be all right."

"no danger to her, sir?"

"none, none; let her go through."

he pulled the lever and the next moment the train tore through the cutting.

"now i think it will be safe to go down again," i said. "i believe i shall be able to get to the bottom of this business."

henderson stared at me aghast.

"do you mean that you are going down again to the tunnel?" he gasped.

"yes," i said; "give me those matches. you had better come too. i don't think there will be much danger now; and there is daylight, so we can see what we are about."

the man was very loth to obey me, but at last i managed to persuade him. we went down the line, walking slowly, and at this moment we both felt our courage revived by a broad and cheerful ray of sunshine.

"we must advance cautiously," i said,

"and be ready to run back at a moment's notice."

"god knows, sir, i think we are running a great risk," panted poor henderson; "and if that devil or whatever else it is should happen to be about—why, daylight or no daylight——"

"nonsense! man," i interrupted; "if we are careful, no harm will happen to us now. ah! and here we are!" we had reached the spot where i had fallen. "just give me a match, henderson."

he did so, and i immediately lit the lamp. opening the glass of the lamp, i held it close to the ground and passed it to and fro. suddenly the flame went out.

"don't you understand now?" i said, looking up at the inspector.

"no, i don't, sir," he replied with a bewildered expression.

suddenly, before i could make an explanation, we both heard shouts from the top of the cutting, and looking up i saw bainbridge hurrying down the path. he had come in the dog-cart to fetch us.

"here's the mystery," i cried as he rushed up to us, "and a deadlier scheme of dame nature's to frighten and murder poor humanity i have never seen."

as i spoke i lit the lamp again and held it just above a tiny fissure in the rock. it was at once extinguished.

"what is it?" said bainbridge, panting with excitement.

"something that nearly finished me," i replied. "why, this is a natural escape of choke damp. carbonic acid gas—the deadliest gas imaginable, because it gives no warning of its presence, and it has no smell. it must have collected here during the hours of the night when no train was passing, and gradually rising put out the signal light. the constant rushing of the trains through the cutting all day would temporarily disperse it."

as i made this explanation bainbridge stood like one electrified, while a curious expression of mingled relief and horror swept over henderson's face.

"an escape of carbonic acid gas is not

an uncommon phenomenon in volcanic districts," i continued, "as i take this to be; but it is odd what should have started it. it has sometimes been known to follow earthquake shocks, when there is a profound disturbance of the deep strata."

"it is strange that you should have said that," said bainbridge, when he could find his voice.

"what do you mean?"

"why, that about the earthquake. don't you remember, henderson," he added, turning to the inspector, "we had felt a slight shock all over south wales about three weeks back?"

"then that, i think, explains it," i said. "it is evident that pritchard really did climb the rocks in a frantic attempt to escape from the gas and fell back on to these boulders. the other man was cut down at once, before he had time to fly."

"but what is to happen now?" asked bainbridge. "will it go on for ever? how are we to stop it?"

"the fissure ought to be drenched with

lime water, and then filled up; but all really depends on what is the size of the supply and also the depth. it is an extremely heavy gas, and would lie at the bottom of a cutting like water. i think there is more here just now than is good for us," i added.

"but how," continued bainbridge, as we moved a few steps from the fatal spot, "do you account for the interval between the first death and the second?"

"the escape must have been intermittent. if wind blew down the cutting, as probably was the case before this frost set in, it would keep the gas so diluted that its effects would not be noticed. there was enough down here this morning, before that train came through, to poison an army. indeed, if it had not been for henderson's promptitude, there would have been another inquest—on myself."

i then related my own experience.

"well, this clears wynne, without doubt," said bainbridge; "but alas! for the two poor fellows who were victims. bell, the

lytton vale railway company owe you unlimited thanks; you have doubtless saved many lives, and also the company, for the line must have been closed if you had not made your valuable discovery. but now come home with me to breakfast. we can discuss all those matters later on."