Beneath the streets, She slumbers.

Beneath the fitted carpets and the padded offices, past the locked and bolted doors of this world, below and behind and beyond everything we have created, something monstrous dwells. Underneath the thin veneer laid upon the world that we, out of hubris, call civilisation, she slumbers. Patiently, inexorably, she slumbers.

I know this. For my sins, I have seen the truth for myself. I have followed the trail of clues, uncovered the secrets, and piece by piece constructed a picture of the lurking nightmare beneath us.

I have plumbed too far, looked into things I should not have, and I pay the price now.

We call it the City. Just the City. When there's only one game in town, you need no other names, and there are no cities like the City. The seething mass of a million busy souls, all living, breathing, eating, working, driving, talking. Laughing, loving, crying, dying, and none of them paying any more attention to the City itself than they do the beggars who dot the streets, unshaven, ragged and hungry.

See the City. Feel it breathe.

It was built, the history books will tell you, starting from a ford on the great River, which became a bridge, which found tollbooths, a hamlet, a market square, a metropolis. It grew fat, you will read, on taxes from merchant shipping and on providing travellers with the sustenance they needed.

And then the City hit critical mass, and people would live in the City merely for the honour of living in the City, because the City was where everything was happening. The City's export became ideas. People bought and sold money in the future for money in the present, traded in thoughts and notions and beliefs and all the things that go with them.

The merchants of hopes and dreams went about their lives, not stopping once to think where the dreams came from. Believing, perhaps, in their pride, that they had invented the marvels they imagined, that they wielded with expert ease.

Beneath the streets, She slumbers.

As for my part in this? I am a simple surveyor. I work for the Council in a simple office; I go home to a small but tidy flat; I watch what I eat, am clean-living and polite. I am unextravagant in my tastes and have a reasonable amount of money saved away for my retirement, though I am not so puritanical that I don't take time to enjoy myself. I have not yet met the woman of my dreams.

It is an inevitable consequence of life in any office that a large proportion of one's work involves correcting the mistakes of others. When more than one man is working on one job, there will always be information that is not passed over. It is one of the unavoidable costs of scaling. Thus it was that on a pleasant Thursday afternoon I worked my way through a folder of street plans, ticking down a list on a piece of paper as I verified each to be correct.

I paused. There was an error. Wapping Street had three manholes entered on it, but - according to the map on my wall - there were only two sewer tunnels running underneath it.

These things happen quite a lot. We get through quite a lot of temporary workers and not all of them put their minds to the job like a professional. It takes dedication to survey a city's sewer system for a living. Not a lot of the young have that. Not a lot of people at all, in fact. Nobody takes pride in their work these days, they just hide their problems under the couch for the next person to deal with.

I placed the pencil carefully in my desk-tidy and checked the map. It was a recent one, but not recent enough that there might not have been a new sewer built since. I would have to check the archives in the basement. I'd been planning to go home early.

We keep all the old files in the basement. Paper copies of everything. They've been trying to start converting to digital, but I've never seen the point myself. Sure, it'll save a little space, but there's no soul in digits, not like with a proper archive. Nobody visits the basement much, so it's not kept heated and it's silent as the tomb. As you climb down the stairs to the aisles of towering filing cabinets it feels, in an odd kind of way, like stepping underwater: you can almost feel the data lapping round your ankles, then around your waist, and finally closing over your head. I like it there, but that day I'd wanted to meet Nigel down the pub, so I hurried.

The files just confirmed what I thought. There'd only ever been two manholes built in Wapping Street. I smiled and hurried upstairs, wincing slightly as my migraine suddenly returned. At least I could finish this off. I stapled the Data Correction Note to the folder and walked to the Grey Goose.

My migraine was back in full force the next day. There must have been something wrong with the beer - I hadn't had that much, and yet I barely slept at all. Three times I awoke, convinced that there was someone in the room with me. The day's work just made things worse.

Mistakes, you see, have a way of propagating across records. People don't take care, they don't check data, they just assume it's right. My extra manhole had done just that. Our latest bill showed three manhole replacements on Wapping Street; it had even somehow appeared on our streetmaps. But it couldn't exist. There wasn't anywhere for it to go down to.

The only answer was to check older records. Lo and behold, it had been built. It had been built at the same time as the second sewer. According to the records, the manhole above that sewer had never been built. It didn't exist.

The migraine twinged. I didn't want to spend the weekend at work. I wanted to do some gardening and maybe buy a new cardigan.

I pulled some more records from the filing cabinets. None of them had Data Correction Notes attached. None of them! Many had the numbers smudged and obscured. A lot of them were missing. A few had even been torn. I'd thought our system had been built on solid foundations. I'd trusted it. It had betrayed me.

At that moment the dull ache that had been building behind my eyes blossomed into red, agonising pain. My vision went. I clutched on to one of the metal cabinets to steady myself, realising that I now had no idea at all which way was up or down.

It was then that I saw Her for the first time. A passing impression was all I received, a flash, a fading vision that was all afterimage. A face, beautiful and oblivious, illuminated with a cold, eerie green light, pitted with scars, ancient and timeless and asleep.

Sight returned. My mind, still tortured from lack of sleep, had played a trick on me. The data room no longer seemed welcome. It seemed suffocating and claustrophobic. I had a terrible vision of the topmost drawer of one of the cabinets sliding out, overbalancing, tumbling like an avalanche and trapping me under piles and piles of dead paper.

Walking as calmly as I could fake I climbed the stairs, wanting to suck in huge lungfuls of fresh, free air.

"Find what you were after, love?" asked the receptionist. I smiled a pale grin.

Friday night brought no rest, nor Saturday. Sleep came only in brief snatches between unsettling dreams. Brick tunnels, pipes, the unseen roots of the city. Corridors boarded away and forgotten. And beneath it all, something great and terrible, sleeping, dreaming, waiting.

This was getting worse and I would have to do something. I didn't want to go back to my doctor. I didn't want to be put on another course of pills, not after I'd been doing so well without, not after what they'd done to me.

Sunday lunchtime, and I told Nigel as much while we watched the match. He's a good friend, is Nigel. He works in construction and maintenance, one of the people who oversee the safety of the tunnels I catalogue. He's the only person I know in the south who supports Newcastle, he's the only person I've ever met who has honey on chips, and he's been with me through a lot -- the first course of pills, for a start. If there's one person I can rely on for advice it's Nigel.

"Take a holiday." he said. "Let someone else sort this out. You're overworked, there's no wonder you're losing it over this. Trust me, there's some things you're better off just walking away from."

And then there are some things that we just won't ever agree on. Walk away from it? He actually expected me to turn my back on my work just like that? I couldn't do that.

There's a time past which you can't rely on records. There's a time past which you need to take action. With one set of records saying one thing and another set saying another, what I needed was results from the field. On Monday Morning I phoned through to the depot and arranged for a survey team to check the area.

Now the depot are terrible people. They'll promise you a report on the phone at noon and then the van will break down, the driver will get lost, or the forms will get mislaid, and you won't hear from them until the evening. So when I didn't get an answer to my problem I didn't call Eric straight away; I took some more paracetemol and waited another hour. And another. I tried to finish my report on the distribution of emergency slurry venting valves in the east district -- work like that was piling up now -- but this headache was stopping me from thinking at all. Nothing made sense. All I could do was concentrate on the dull, throbbing ache behind my eyes.

Tuesday morning. Another night without sleep. Catching myself in the mirror in the morning made me realise just how bad I was looking. My eyes were bloodshot and sunken. This was no good, I would have to take the day off and recover, or I'd not be able to do my job at all. Maybe I would have to go and see the doctor anyway. I could wait until tomorrow to find out what the surveyors had found.

The phone rang. It was work. The surveyors had vanished. All of them, without a trace. Their van had been clamped and would be towed away if we didn't move it.

Enough of this. I was fed up, sick and tired of getting answers that made no sense. I was fed up of this blinding headache and the erratic blackouts. I pulled on yesterday's clothes and my coat, searched under the stairs for a decent-sized torch and drove to Wapping Street myself.

Maps never really give you the right impression of a place. Not until you've been there yourself. What on my map had been two lines with the words "WAPPING STREET" down the middle was, when I arrived, a valley in concrete, nestled between a shoe factory and a meat warehouse in the City's run-down industrial area. The survey van was still there and, yes, it was parked on double yellow lines and its wheel had been clamped. This was the main reason it hadn't been driven away yet, because the doors had been left unlocked and open. The inside, of course, had been emptied of anything that could be sold. And, most curious of all, the manhole cover -- the third manhole cover -- was invitingly open.

I dropped the torch into my coat pocket and climbed down. Part of me felt young again. I thought back to my days as an engineer, when I'd be doing this all the time. Part of me instead thought back to the first time I'd spoken to the doctor, when I'd shown Nigel the traps I'd set to catch the murderers who hid in my allotment and when he'd insisted I speak to somebody about it. What was I doing? What was I thinking? Wasn't I supposed to make an appointment and report the first signs of exactly this thing? But instead all I did was flash on the torch and step down the tunnel, observing the old brickwork painted over with cream gloss like a wall in a sports centre, and pipes running alongside the walls.

One thing was for sure. This wasn't a sewer tunnel. I've worked as a sewer safety engineer, like I said, before I quit the job to move to something office-based for the good of my health. Sewer tunnels aren't painted, they drip, and they smell... well, they smell like shit, as you might expect. This place smelled of oil, of machinery, and of a smell that I couldn't quite place, somewhere between leafmould and rust.

A clipboard had been dropped on the floor. Ahead, a hard hat. Most of the pages were ripped out, but the top one remained. Confirm: Three manholes, only two tunnels. Confirm: Two manholes lead to sewer tunnels XJ-13 and XJ-14. Third manhole leads to unmapped tunnel, no Department of Public Health ID. That had been as far as they had got.

The tunnel ended at a door. No, not a door -- a bulkhead, like the ones on a ship. This, too, had been painted over -- even over the gap between the bulkhead and the wall, so that the paint would have to be chipped off for the door to open. It looked like somebody had tried, too. They'd gotten about halfway down, and then...

Oh, no.

About halfway down, about where the chipping finished, were a few specks of red. Barely any at all. Somebody had made them stop. I stepped back, fighting an overwhelming desire to be sick, shining my torch back down the passage to see if anybody was coming.

Nobody. I really didn't see what choice I had. I began to scrape the rest of the paint off, straining to hear for footsteps above the steady thrum of underground mechanics -- maybe a boiler, or a pump, or something. It was a paralysingly terrible thing to know that at any moment somebody might lower themselves into the other end of the corridor, raise a pistol and finish me, but what was really terrible of the prospect of not finding what was behind the door: what was so special that men had killed to keep it a secret.

At last I was done. I turned the wheel and pulled the great door open, dislodging clouds of old rust as it went.

One day I might be able to forget what was on the other side, in that silo, that deep, circular chamber longer than streets and deeper than mountains. One day I might wipe from my mind the intense vertigo as I looked down into blackness from the catwalk I stood on. And if I am very lucky then one day, one day I may no longer remember the moment when my perception changed, when I realised that the colossus beneath the city, the statue of the peacefully sleeping woman from my vision, so huge that it filled the chamber, so gargantuan that I could, if I wished, comfortably stand in one eye-socket, was not a statue at all but a living creature of flesh and blood.

I'm not sure how long I stood there, how long I goggled, paralysed by the utter impossibility of what I was seeing. How long I considered back and forth the merits of pitching myself over the safety-rail of the catwalk I was on just to escape the horror of living in a reality where the creature I saw before me, the great Sleeper beneath the City, was real. What was reality, after all? Forty years I'd lived in a world where this was impossible. How much else of what I'd thought was real was a lie? Was this even happening to me?

"I told you to give it up." said Nigel, crossing the catwalks from the other side of the room. "I warned you. I tried to help you, Owen, before it was too late." There was a despairing look now across his thin face and I thought back to all the times I'd seen him in the past -- ever since I'd moved to an office job and he'd taken over my old work -- and to the way that more and more he seemed to be a weight upon his shoulders. "Nobody deserves to have to see Her unprepared. Let alone twice."

Then it hit me. I had been here before. The episode in my garden hadn't been my first visit to the doctor. My first had been...

"All this used to be a cavern until the construction workers you were overseeing found it. Half of them threw themselves to their deaths there and then when they saw Her. Most of the rest went catatonic on the spot. You were collected enough to get the survivors out and seal the door before anybody else died. I'm sorry, Owen, I'm so sorry that we didn't get to this one before you, but at the time we were a young organisation. We'd only just found the first few ourselves, we didn't have the funds or the power to get under all the cities in the world."

I wasn't listening. I didn't need to. I was twenty years younger, being placed in an ambulance, an oxygen mask over my face, concerned faces all around.

"We're not ungrateful people, really we're not. We got you prescribed medicine that would help you forget, so that you could sleep without the nightmares. You were put into a comfortable desk job and paid well over average wage. We wanted you to have a happy life. It was the least we could do for you after what you had to go through. They even assigned me to keep an eye on you while I continued my work, bricking off the cave and hiding any of the evidence that it, or the Sleeper, ever existed."

My mind refocused. "And the survey team. You killed them!"

That sad, defeated look came to Nigel's face again. "I had to. There was no other way, not once I'd found what they were doing. The Sleeper has to be kept secret, no matter what. Please don't think that it was easy for me. It's the worst thing I'll ever have to do. Killing people never gets easier, not even after twenty years of doing this job."

"No matter what? You think that what you're doing justifies twenty years' worth of killing?"

"Yes." said Nigel simply. "It really does. You don't -- you know that we call these things the Sleepers for a reason, right?"

I stayed silent. Nigel continued. "I expect you're imagining these things waking up and climbing up Big Ben with Fay Wray in their hands. You're wrong. That's not the half of it. We don't know what they're going to do when they wake up, but it doesn't matter. Because what we do know is that they'll stop dreaming. Do you know what they're dreaming about? Cities, Owen, they're dreaming about cities. Each and every one of them is -- and there really are rather a lot: there's a Sleeper under every major city in the world. Cairo. Paris. New York. Moscow. Baghdad. All of them."

Nigel slowly pulled his hand down over the front of his face, something he always did when he was tired and dispirited and didn't like what he was saying. "These things are the reason cities work. The reason that thousands of people can move their homes together, can live the white lie that they're little cogs in a great machine larger than themselves, Owen, is that the Sleepers are dreaming that lie right into their heads."

"I don't care." I said. "You're a murderer and so is everyone you work with. These things have to wake up, and this -- this organisation of, I don't know, Illuminati or Masons or Men In Black or whoever it is who's keeping the secret have to be finished."

"You've not thought this through." said Nigel. "You're hysterical. Seeing one for the first time does that somehow. The second, third few times aren't much of a picnic either, but... no, you're not making a decision like that. You don't have the authority."

I stopped listening, and grabbed for my torch, winding up to throw it in an overarm swing at the pale, beautiful, sleeping face. Nigel rushed forward. He'd been getting closer to me all the time he was talking, and was now near enough to grab my arm, knock the torch out of my hand, and let it fall all the way into blackness. The chamber now was lit only by the wan light of the bulbs on the walls.

"Think about what you're doing, Owen." hissed Nigel. "If that thing wakes up, we lose everything. Everything that keeps people sitting comfortably watching television just a few metres and a thin party wall away from a complete stranger without going insane. Instant riots throughout the whole city. Is that what you want?"

"And your way's better?"

"The Sleeper wakes, Owen, and the whole city goes up in flames. Nobody manning anything. Any nuclear plants? They melt down. All the gas mains explode. Aeroplanes fall out of the sky. When the Sleeper wakes, everybody dies."

I sighed. "Fine. Fine. So what do you propose?"

"I brought some more of the medicene, Owen. Take it. Go back to sleep. Let it help you forget you ever found any of this, and let us go back to handling it. I promise you, I promise this will not happen again."

"And you keep on killing to protect your secret."

"It's the only option."

And I agreed. As far as Nigel would see, it was the only option. Myself, I had other plans. I didn't swallow the pill. I hid it under my tongue and I gulped down. He was so relieved I'd seen sense that he didn't check my mouth: he just got me to a chair, let me pretend to fall asleep, hauled me away and allowed me to wake up in my own bed, where I spat the hateful thing out, rinsed my mouth and spat again.

So now I know the secret, and it's not getting easier like Nigel said it would. I have seen the Sleeper beneath the city, the monstrous, slumbering giant that dwells within our vanity and hubris. I've come to my decision. All that I've been through, all the lies I have endured must not die with me. I have written these words down, so that something can survive me. I have sent copies to such friends as I trust. And, finally, I have prepared to free myself from the torture of what I know. Of the knowledge that all we hold dear, all that we have constructed is no more than a sandcastle before the tide. One day the Sleepers will awake, and the fire will come. I do not intend to be present for that.

The gun is in my desk drawer.