The Hum at Cwm Ddu

I rolled into Pen-y-Ffynnon at around 20:30, hauling a day's worth of cables and cases and a headache that had started somewhere beyond the second ridge. The rented estate car needed petrol, but I needed batteries more. AAAs for my field recorder. I'd been burning through them faster than planned, and the pack I'd brought from Manchester was down to two cells that might have had another hour between them, probably less.

Home Bargains stood just off the high street on a small retail parade, beside a closed building society branch and a kebab shop that seemed to be open despite being dark. I pulled in beneath the flat wash of the car park lights and switched off the engine.

The quiet descended quickly. That was the thing about this place.

Silence had weight here. No hum of mobile masts, no distant dual-carriageway noise, only the wind, my own breathing and the ticking of the cooling engine. I took my wallet and got out. The air smelt of tarmac and something green I couldn't name.

Trees, probably, or simply rural Powys at night.

Inside, the shop was bright and too warm. The sort of heat that catches you after a long drive and makes you feel slightly sick. There were aisles of crisps, motor oil and cleaning products beneath flickering LED strips.

A man about my age stood behind the till in a navy shop fleece, his orange-trimmed name badge sitting crooked on his chest. Callum Price. He glanced up, nodded once and returned to his phone.

I found the batteries near the back, beside the seasonal stock. Leftover Easter baskets had been reduced to almost nothing. I took two six-packs of Panasonic AAAs and a bottle of sparkling water I didn't especially want but thought I ought to drink. My hands smelt of the recorder bag: leather, dust and something metallic from the windscreen.

The transaction took perhaps thirty seconds. Callum rang everything through without saying much. I paid in cash. It had become a habit in the smaller places around here, where card machines could be temperamental or slow.

"Thanks," I said.

"Yeah. That's it."

I'd been in that part of Powys for a week by then. Mair Hughes had rented me a room in her house just outside town. It was on the first floor, clean, with a window overlooking her garden and the gravel drive where I parked the estate car each night. She was polite and distant in the way landladies often were when they were accustomed to temporary people. She hadn't asked much about me on the first day.

The only thing she had required was four weeks' rent and a four-week deposit in advance.

The job was simple. Imogen Clarke, a science journalist based in London, needed clean audio from the Cwm Ddu Radio Quiet Area for a feature she was preparing. The protected zone was administered through UKRI and STFC arrangements. She wanted ambience, recordings of tours at Cwm Ddu Radio Observatory and perhaps a few interviews if I could secure them.

Imogen had hired me for similar assignments before. I worked mainly as a field sound recordist, and this job paid well enough in pounds for a week's work. I liked the place more than I'd expected. No mobile signal meant no distractions, no refreshing my emails, no message threads tugging me sideways. There was only me, the recorder and long stretches of road through hills that didn't care whether I existed.

The observatory itself was strange in a good way. Its immense principal dish, the Cwm Ddu Radio Telescope, pointed towards something I couldn't see. Notices lined the quiet corridors. Everyone spoke softly because that was what you did around instruments sensitive enough to hear the universe breathe.

Gareth Llewellyn conducted the tours. He was an older man, enthusiastic and good at explaining things without sounding as though he were talking down to anyone. I'd already recorded two of his sessions and captured some useful crowd ambience: visitors' questions, footsteps on metal grating and the peculiar muffled acoustics of the visitor centre.

Everything felt narrow out here. Focused. I didn't mind it.

I pushed through the Home Bargains doors with the batteries in a reusable carrier bag and the sparkling-water bottle tucked beneath one arm.

The car park was still empty apart from my estate car and a pickup near the far edge that I hadn't noticed before. Callum's, probably. The lights buzzed overhead, casting a flat orange wash that made everything beneath them look ill.

I was halfway to the car when I saw him.

A man in oil-stained work clothes was staggering out from between two parked cars at the far end of the car park. His gait was wrong.

Not drunk. I'd seen drunk. This was wrong in a way that tightened my stomach before I understood why.

He took three more steps and fell hard beside the kerb.

I stopped and looked back at Home Bargains. Callum was still inside, visible through the glass, his head bent over his phone.

The man didn't get up.

I dropped the carrier bag and ran.

He was lying on his side when I reached him, knees drawn up, one hand clawing at the tarmac. The name written on his work badge in faded permanent marker was Dafydd Morgan.

His clothes looked worse up close. They were stained with oil and perhaps something darker. His face was pale and slick with sweat. His eyes were open, but they weren't tracking properly.

"Hey," I said, dropping into a crouch. "Are you hurt?"

His mouth opened, closed and opened again.

I kept a first-aid kit in the estate car. A small one, the sort you assembled for field jobs in case you sliced your hand on a cable or turned an ankle on rough ground. I didn't know whether it contained anything that would help him, but it was something.

"Hang on," I said. "I'm going to get-"

"Don't."

His voice came out wet and strangled. I froze.

Don't what?

He jerked all over. It wasn't quite a seizure. The movement looked voluntary and involuntary at the same time.

His eyes rolled upwards and fixed upon something over my shoulder. I turned.

There was nothing there. Only the empty car park and the dark hills beyond the lights.

"Don't," he said again. "Don't listen."

That unsettled me. I looked back towards the shop.

Callum had moved to the window. He was staring out, his phone still in his hand. I waved to him. He didn't move.

Dafydd made a sound halfway between a gag and a gasp.

I turned back. His hand shot out and seized my wrist. His grip was stronger than I'd expected from someone who looked close to unconsciousness.

"When it hums," he said, "don't turn towards it. Don't look for where it's coming from."

"When? What hums?"

"Just..."

He coughed and released my wrist. His hand returned to the tarmac, his fingers scraping it in short, stuttering drags.

"Just don't."

I didn't know what to do with that.

His eyes had begun tracking again, looking up and to the left, following something I couldn't see. His jaw worked, but no sound emerged. Then his entire body stiffened and he sucked a sharp breath through his teeth.

"All right," I said, keeping my voice level. "I'm going to get help. You're going to be fine."

I didn't know whether that was true, but it was what you said.

I stood and turned towards Home Bargains. Callum was still at the window. I waved again, more urgently this time, and he finally moved. He unlocked the door and stepped halfway outside.

"Call 999," I shouted.

He only stared.

"Call them now."

That got him moving. He ducked back inside.

I crouched beside Dafydd again. He was still lying on his side, twitching and staring at nothing. His breathing was fast, shallow and wrong. I didn't know what I was seeing. A stroke, perhaps. An overdose. Something neurological I didn't have a name for.

"Help's coming," I said.

He didn't respond.

I pulled the recorder bag from my shoulder. It was a stupid impulse. I still don't know why I did it, except that my hands needed something to do and I couldn't simply kneel there watching him come apart.

Dafydd's mouth moved again. I leant closer.

"Listening," he said, scarcely above a whisper. "They're listening."

"Who is?"

"Don't know. Can't... can't stop it."

His hand rose again, slower this time. He pointed at his own head and tapped his temple twice.

"In here," he said. "Won't stop."

I hadn't said anything. What could I have said to that?

He twitched again, harder. His eyes rolled back, and for a moment I thought he was seizing. Then they snapped forwards and locked on mine.

"You hear it?" he said. "You're already gone."

Then he stopped speaking.

I pressed two fingers to the side of his neck. I had to move closer because his collar was stiff with grime, and at first I couldn't find the right spot. His pulse was there, fast and uneven, fluttering in a way that troubled me more than simple racing would have done.

His breathing was shallow but steady enough. I counted four breaths while keeping my fingers against his neck. In through clenched teeth, out through barely parted lips. His eyes remained open, but they no longer tracked me. They kept sliding upwards and to the left, following something I couldn't see.

"All right," I said.

I didn't know whether he could hear me.

"You're all right. Help's coming."

Dafydd's hand twitched against the tarmac. His fingers scraped in short, stuttering drags, as though he were trying to pull himself somewhere but couldn't make the rest of his body cooperate.

I looked back at Home Bargains. Callum was inside with the phone pressed to his ear, pacing behind the till. Even through the window I could see his mouth moving quickly.

Dafydd made another low, choked sound.

When I turned back, he was staring directly at me. The desperate focus in his eyes made my stomach drop.

"Don't."

His voice was wet. He coughed and tried again.

"Don't turn towards it when it hums. Don't look for where it's coming from."

"When what hums?"

I kept my voice calm and level. I thought that was what you were meant to do.

His jaw moved. For several seconds, nothing came out.

"You'll want to..."

"Turn towards it?"

He nodded, barely.

His whole body was trembling now, fine vibrations passing through him as though he were freezing, although his face remained drenched in sweat.

"What am I listening for?" I asked.

Dafydd opened his mouth, then closed it. His hand came up and tapped his temple twice, just as before.

"Starts quiet. You think it's..."

He broke off with a grimace.

"You think it's something else? Something normal?"

I didn't know what to say. I merely nodded.

"But it's not," Dafydd said.

His voice sank until it was almost inaudible. I had to lean close to hear him.

"It's not normal. And once you turn, once you look..."

He stopped.

His gaze lost focus again and drifted upwards and to the left.

"Once you look, what?"

Nothing. His breathing hitched. His hand dropped back to the tarmac and resumed its clawing motion.

I heard the shop door open.

"They're coming," Callum called across the car park. "They said about ten minutes."

Ten minutes.

I looked down at Dafydd. His lips were moving, but no sound came out. I couldn't tell whether he was trying to speak or whether it was involuntary.

"Dafydd, stay still," I said. "Don't try to move."

His eyes snapped back to mine. For a second, he looked almost lucid. Almost present.

"Tell them," he said, clearly enough that I didn't need to lean closer. "Tell them I heard it three days ago. Started soft."

"Started soft," I repeated. "All right. What did you hear?"

"Humming."

Dafydd's whole face twisted.

"Thought it was the fridge at work. The one in the fitters' room. Thought it was... doesn't matter. It wasn't."

He dragged in a breath through his teeth.

"Gets louder. Gets inside."

"Inside where?"

He tapped his temple again, harder this time. Hard enough to hurt.

"Won't stop. Can't make it stop."

I wanted to take his hand and prevent him from striking himself again, but I didn't know whether I should move him at all. So I remained crouched beside him on the cold tarmac, my recorder bag lying a few feet away and the reusable carrier somewhere behind me.

"They're coming," I said again. "You're going to be fine."

Dafydd laughed. It sounded broken and wrong.

"No," he said. "No, I'm not."

Then his back arched. His eyes rolled upwards and his whole body went rigid, hands curling into fists as his heels scraped against the tarmac.

"Hey!"

I reached out, my hand hovering above his shoulder.

"Stay with me."

He didn't respond. His jaw was clenched so tightly that I could see the muscles jumping in his neck. His whole body shook and then became still. Not relaxed. Merely still. Locked in place.

I heard the siren before I saw the lights. It was faint at first, then louder as it cut through the silence. I stayed where I was. I didn't know what else to do.

The ambulance entered the car park quickly, its siren cutting off in the middle of a wail. Two paramedics climbed out. The first was a man in his early thirties, perhaps, with dark hair and a green uniform marked with Welsh Ambulance Services University NHS Trust insignia and reflective strips. The second was a woman with auburn hair tied in a ponytail, wearing the same uniform.

They moved quickly but without panic. Controlled.

The man reached us first. He dropped a response bag beside Dafydd and crouched opposite me.

"What happened?"

"He collapsed," I said. "About five minutes ago. He was walking, then he just went down."

"Did he hit his head?"

"I don't think so. He was already on the ground when I reached him."

The woman knelt beside Dafydd's legs, her fingers already pressed to his wrist.

"Pulse is rapid and thready," she said.

Her voice was calm and steady.

The man leant over Dafydd and checked his pupils with a small torch.

"Dafydd, can you hear me?"

There was no response. Dafydd's eyes were half open but unseeing, and his breathing had become ragged.

"Do you know any of his medical history?" the paramedic asked me.

"No. I don't know him. I was just..."

I gestured vaguely towards Home Bargains.

"I saw him fall."

"All right."

He looked at the woman.

"Let's get oxygen on and move him."

They worked quickly. An oxygen mask went over Dafydd's face and a blood-pressure cuff around his arm. I moved back several steps to give them room, but I didn't leave.

The woman's name badge read Bethan Rees. She spoke to Dafydd in a low, reassuring voice despite receiving no response. The man, Rhys Parry, called out observations I only partly understood: pulse, blood pressure, oxygen saturations at ninety-one per cent, reduced response on the Glasgow Coma Scale.

They brought the stretcher from the ambulance and transferred Dafydd onto it with smooth, practised movements. Straps went across his chest and legs, and the oxygen cylinder was secured at the side.

I followed as they wheeled him towards the ambulance. Rhys glanced back at me.

"Are you travelling with him?"

"No, but he said something before you arrived."

Rhys stopped and turned.

"What did he say?"

"He kept talking about a humming sound. Said he'd first heard it three days ago. Said it got louder and got inside his head."

I tried to remember his exact words.

"He said, 'When it hums, don't turn towards it. Don't look for where it's coming from.'"

Rhys's expression didn't change. He gave a single nod.

"All right. Anything else?"

"He said, 'Once you turn, once you look...' Then he stopped. He didn't finish, but he was frightened."

Bethan was already inside the rear of the ambulance, reaching down to guide the stretcher. Rhys watched me for another second and nodded again.

"Thank you."

They loaded Dafydd, closed the doors and drove away with the siren sounding again. Red and white light swept across the empty car park.

I stood there for a minute, perhaps longer. Callum remained in the Home Bargains doorway, staring after the ambulance.

I picked up my recorder bag and found the reusable carrier with the batteries and sparkling water still inside. Then I got into the estate car and drove.

Dyffryn Memorial Hospital was small, a single-storey building of pale brick lit too brightly against the darkness. I followed signs to the A&E entrance and parked near the ambulance bay.

I didn't know why I had gone there. I thought I would give them a few minutes, then go inside and see whether there was anything else they needed to know. If Dafydd had family, someone needed to contact them. Something.

The ambulance was already backed up to the bay doors when I got out and walked over.

Rhys and Bethan were wheeling Dafydd inside. I could see him strapped to the stretcher, the oxygen mask still covering his face. He wasn't moving.

I followed them through the automatic doors into a bright corridor that smelt of disinfectant and floor polish.

A nurse in NHS navy scrubs looked up from a desk and moved towards the stretcher. Her name badge read Carys Vaughan.

"What have we got?" she asked.

Rhys began delivering a rapid handover. An unresponsive man in his mid-forties, found collapsed in a car park, observations unstable.

I remained a few steps behind them, just inside the doorway.

A doctor came around the corner. He was older, with a neat moustache, dressed in shirtsleeves with an NHS lanyard around his neck. His badge identified him as Dr Alastair Pritchard. He went directly to the stretcher and began examining Dafydd, his hands quick and efficient.

I took another step forwards. Carys looked up and noticed me.

"Are you family?" she asked.

"No. I'm the person who found him."

"All right."

Her voice was polite but firm.

"We've got him from here. You can wait in the reception area if you'd like."

"I told the paramedic what he said before he stopped talking. I only wanted to make sure-"

"We have the information."

Carys stepped between the stretcher and me. She wasn't aggressive. She simply became a wall.

"Reception is back through those doors and to your left."

Dr Pritchard was already moving Dafydd further down the corridor. Rhys and Bethan followed with the stretcher. Carys stayed where she was, watching me.

I nodded and stepped back.

"All right."

She waited until I turned away, then followed the others.

I walked outside, got into the estate car and sat for a minute with my hands on the steering wheel, staring at the illuminated A&E entrance.

A sick, unfinished feeling settled in my chest. The sort you get when you know something is wrong but can do nothing about it. When the pieces don't fit and nobody is asking you to explain why.

I drove back to Mair's house, let myself in through the side door, climbed the stairs to my room and sat on the edge of the bed without switching on the light.

It was nearly midnight. I should have been tired. I wasn't.

My phone rang at 04:37. I'd been asleep for perhaps an hour. I snatched it from the bedside table and squinted at the screen.

Owain Mercer.

Owain lived locally and was retained as an on-call community responder, as well as doing occasional maintenance work for observatory contractors. I'd met him through the house where I was staying, and he had a habit of hearing local news long before it reached anyone else.

I answered.

"Yeah?"

"You awake?"

Owain's voice was low and careful.

"I am now."

"You were at the hospital tonight. Dyffryn Memorial."

It wasn't a question.

I sat up.

"How did you know?"

"Word gets around."

He paused.

"The man you brought in, Dafydd Morgan. He didn't make it."

I said nothing.

"He became unresponsive on the way in," Owain continued. "They tried to resuscitate him, but they couldn't."

I rubbed my face with my free hand.

"When?"

"Maybe twenty minutes after they got him inside."

Twenty minutes. I had still been sitting in the hospital car park.

"Do they know what happened?" I asked.

"Not yet."

Owain lowered his voice further.

"But I'm hearing things, and I need you to listen."

"All right."

"Dafydd isn't the first. There have been others. The same thing. The same..."

He stopped. I heard him take a breath.

"The same sort of symptoms."

"What symptoms?"

"Disorientation. Paranoia. Talking about sounds nobody else can hear."

Another pause.

"Then they collapse. Then they die."

I thought of Dafydd tapping his temple. The humming gets inside.

"How many others?" I asked.

"Three that I know of, over the past eight months."

"Jesus."

"Yeah."

Owain was silent for a moment.

"Look, I don't know exactly what you're doing here beyond the recording work, but if you're planning to stay, you need to be careful."

"Careful how?"

"Pay attention. If you hear something that doesn't make sense, don't try to find out where it's coming from. Don't go looking."

I almost laughed. It came out badly.

"That's what Dafydd said. Don't turn towards it. Don't look for the source."

Owain fell silent.

When he spoke again, his voice was flat.

"He told you that?"

"Yes. Just before the ambulance arrived."

"Shit."

He exhaled hard.

"All right, listen. I've got to go, but watch yourself."

"Owain-"

He had already ended the call.

I sat in the darkness with the phone in my hand. Outside, the sky had begun to lighten, grey creeping in around the edges.

I kept replaying it. Dafydd's eyes tracking something I couldn't see. His wet, desperate voice.

When it hums, don't turn towards it. Don't look for where it's coming from.

He had been responding to something. Something real enough to kill him.

And I had been right beside him in that car park. I hadn't heard a thing.

Owain sent me a message at about 11:00 the following morning. It said only: Post Office. Twenty minutes.

I was still at Mair's house, sitting on the bed with the recorder bag beside me. The batteries I'd bought from Home Bargains remained unopened in the reusable carrier on the floor, along with the bottle of sparkling water. I'd hardly moved since Owain's call at 04:37.

I drove into Pen-y-Ffynnon and parked near the village Post Office. It was a small brick building with a Royal Mail sign above the entrance. A Welsh flag moved in the breeze outside the neighbouring council office. Two cars stood in the gravel car park.

Owain was leaning against his pickup at the far edge, his hands in his jacket pockets. I got out and walked over.

"Hello," I said.

He nodded. For a moment he said nothing, merely studying me before looking beyond me towards the road.

"Are you all right?" he asked.

"Yes."

He didn't look convinced.

"You didn't know him, did you? Dafydd?"

"No. I only saw him collapse."

Owain nodded again. He took one hand from his pocket and rubbed the back of his neck.

"I heard some things this morning from inside the hospital."

I waited.

"They did a CT and then an MRI," Owain said. "The staff who saw the images were shaken."

"Shaken how?"

Owain looked at me again. His expression was careful and guarded.

"The scans showed that his inner-ear structures were absent."

For a moment, I said nothing. I simply stood there.

"Absent?"

"As if they'd never existed. Clean. No damage, no scarring, no evidence of an operation or trauma. Just... not there."

I thought about Dafydd lying on the tarmac, his hand repeatedly rising to his temple. It gets inside. In here. Won't stop.

"That doesn't make sense," I said.

"No," Owain replied. "It doesn't."

"People don't simply lose their inner ears. Not like that."

"I know."

I looked towards the Post Office and the Welsh flag stirring in the wind. I tried to fit what Owain had told me to what I had witnessed in the car park. I couldn't.

"Did they say what caused it?"

"No. I don't think they know. Someone suggested a birth defect, but..."

Owain shook his head.

"Dafydd was forty-six. He'd worked as a forestry machinery fitter for fifteen years. If he'd been born without those structures, somebody would have noticed long before now."

That was true. I knew little about inner-ear anatomy, but enough to understand that it was essential to hearing and balance. Dafydd had been walking when I saw him. Staggering, but walking. He had lived and worked normally for decades.

"So what?" I asked. "They simply disappeared?"

Owain didn't answer. He only regarded me with the same guarded expression.

I rubbed my face. My hands smelt of the steering wheel and something stale I couldn't identify.

"Does this have anything to do with the other three cases you mentioned?"

"I don't know," Owain said. "I haven't heard anything about their scans. Only that the symptoms matched. Disorientation, nausea, paranoia, sounds nobody else could hear. Then an apparently unrelated collapse or accident."

I considered that and tried to find a pattern. I found nothing.

"Do you think it was drugs?"

Owain shrugged.

"Maybe. But I've seen people on crystal meth, prescription tablets and plenty else. This doesn't look like that."

"An infection?"

"Could be."

He didn't sound as if he believed it. Neither did I.

We stood there for a while. A car passed slowly along the main road and disappeared around the bend.

"Why are you telling me this?" I asked.

Owain looked at me.

"Because you were there. Because you heard what he said. And because if this is something that's spreading, you ought to know."

"I'm only here for a job," I said. "Recording clean audio. That's all."

"I know."

"I'm not investigating anything."

"I didn't say you were."

The way he watched me made it clear that he thought I should pay attention regardless.

"Just be careful," Owain said. "That's all."

He climbed into his pickup and drove away.

I remained there another minute before returning to the estate car. I sat with my hands on the steering wheel, in the same position I'd occupied outside the hospital the previous night, with the same unfinished feeling inside me.

Dafydd's inner-ear structures were missing. I didn't know what to do with that.

I went back to Cwm Ddu Radio Observatory the next morning and told myself I had work to finish. Imogen wanted more recordings: ambient sound, visitor interactions and perhaps another tour if Gareth was conducting one. I had a job. I needed to do it.

I parked beside the visitor centre at 09:45. The car park was already half full. There were families, a couple of older visitors carrying expensive cameras and a school party gathered beside a hired coach.

I took the recorder bag and went inside.

Gareth stood at the front desk speaking to a woman with a clipboard. When he saw me, he smiled with the same friendly tour-guide expression he'd given me on the previous two occasions.

"Back again," he said.

"Yes. Imogen wants some more material."

"We've got a tour starting in fifteen minutes, if you'd like to join us."

"That works."

I paid at the card machine and received an adhesive visitor pass. I stuck it to my jacket and checked my levels while I waited.

I plugged in the headphones, pressed record and tapped the windscreen twice. The signal was clean. No hum, no interference, only the taps and the low ambient wash of conversation in the lobby.

I kept the headphones on and listened.

Footsteps on tiles. A child asking his mum whether they would be allowed to see the telescope. The hiss of the coffee machine behind the counter.

All normal. All exactly as expected.

But I was listening differently now. I wasn't merely capturing sound for Imogen. I was checking it, as though something might be hidden in the files. Something I had been trained to notice but had missed.

That was stupid. I knew it was.

Dafydd's collapse had nothing to do with my recordings, the radio-quiet area, the observatory or anything else I was working on.

I kept listening anyway.

The tour began at 10:00. Gareth led the group outside towards the principal instrument, the Cwm Ddu Radio Telescope, or CDRT, the immense dish everyone had come to see. I stayed near the back with the recorder running and the bag strap across my chest.

Gareth went through his usual routine. He explained how the telescope worked, how it received radio waves from space and how the Cwm Ddu Radio Quiet Area protected it against interference through statutory radio-protection powers and restrictions administered with UKRI and STFC involvement.

He used the same analogies and jokes as before, delivered with the same practised enthusiasm. The visitors asked much the same questions.

How far could it see?

What was the biggest thing it had discovered?

Could they go inside?

Gareth answered each question patiently, offering safe explanations that made nobody uncomfortable. I recorded him and tried to concentrate on the job, on capturing clean audio, on doing what Imogen had hired me to do.

But I kept thinking of Dafydd. His hand rising to his temple. His insistence that the sound got inside. Owain telling me that the structures of his inner ears were gone as though they had never been present at all.

The tour continued into the control room. Gareth explained the monitors, the data streams and the methods scientists used to analyse signals.

A child asked whether they had ever heard aliens.

Gareth laughed.

"Not yet," he said, "but we're listening."

I adjusted the gain and kept recording.

When the tour ended, I remained in the lobby for another twenty minutes, capturing ambient sound. Footsteps, voices, the coffee machine and the soft electronic beep of the card machine at the desk.

Everything was clean. Everything was normal.

I packed the equipment, returned to the estate car and sat in the driver's seat with the recorder bag on my lap.

Dafydd Morgan was an extraordinary isolated case. That was what I kept telling myself. Perhaps it had been drugs. Perhaps an infection. Perhaps some congenital condition that nobody had discovered until it killed him.

But the missing inner-ear structures wouldn't release me. They didn't fit. None of it fitted.

I opened the recorder bag and removed the handheld unit. I scrolled through the files. Three tours with Gareth. Two ambient sessions in the visitor centre. One exterior recording of the telescope itself, containing only wind, distant machinery and the faint creak of metal.

I plugged in the headphones and checked a section from a file recorded two days earlier.

Gareth's voice explaining radio astronomy. Visitors' questions. Footsteps on metal grating.

Nothing unusual.

I checked another file, then another. They were all clean.

I didn't know what I was seeking. I didn't even know whether there was anything to find, but I continued looking.

By the time I returned to Mair's house, it was nearly 17:00.

The commission was finished. I had enough material for Imogen, enough clean audio for whatever feature she was writing. Yet the suspicion remained, turned higher now, louder than it had been that morning.

I sat on the bed and stared at the recorder bag on the floor and at the reusable carrier beside it, still containing the unopened batteries and sparkling-water bottle.

Dafydd's inner ears were missing. I didn't know what that meant, but I knew I wasn't going to stop thinking about it.

That night I sat on the floor of my room at Mair's house, the recorder bag open in front of me and the handheld unit connected to my headphones.

The work was done. I had already told myself that twice. I had enough material for Imogen Clarke's feature: tours, ambience, the visitor centre and the atmosphere of the protected zone. All of it was clean and usable.

But I wasn't packing.

I sat cross-legged on the wooden floor with my laptop beside me and the files queued in the order in which I'd recorded them.

I began with the exterior recordings from three nights earlier.

Wind moving across the telescope structure. The distant tree line. Faint metal creaking from the dish itself.

I closed my eyes and listened to the entire six-minute file. Nothing unusual. Only what I had captured: night air, a low breeze and the sort of clean ambience available only in a place without ordinary radio interference.

I moved to the next file, another night recording from the same session. I had made this one near the visitor centre after hours, once the car park had emptied. I'd placed the recorder on the bonnet of the estate car and allowed it to run for ten minutes while I stretched my legs.

The sparkling water I had bought before Dafydd collapsed had remained among my belongings. I hadn't opened it at the shop. The bottle now stood beside my bed with only a couple of sips missing.

The file played. Wind again. A car passing along the access road perhaps half a mile away. Gravel shifting under my boots when I returned to collect the recorder.

Then, in one of the quiet intervals, I caught something.

A low tone. Barely there.

My headphones almost failed to reproduce it. It sat at the edge of the audible range, deep enough that I felt it more than heard it.

It pulsed rather than remaining steady. Four seconds on. Four seconds off. On, off, on, off.

I went back and played the section again.

There.

It resembled a distant idling engine or a generator running far away, except there was no generator near the visitor centre. I knew that. On my first day, I had asked Gareth whether there was any mechanical noise I needed to account for, and he had said no. The entire site was designed to operate quietly.

I leant forwards and pulled the laptop closer, opening the waveform in my editing software. The tone appeared as a faint thread along the bottom of the display, just visible when I enlarged it.

A consistent pulse. A low-frequency signal centred at 37 Hz. Four seconds on and four seconds off.

I checked the metadata.

Recorded at 23:23. Low wind speed. No precipitation.

I opened the next file from the same session, captured at a different location near the edge of the car park and the tree line. I skipped to a quiet passage and listened.

The same tone. The same 37 Hz pulse. Four seconds on, four seconds off.

For a minute, I didn't move. I sat with the headphones on and the waveform glowing on the screen before me.

Then I started opening older files.

The first time I'd recorded anything after dark had been five days earlier. I'd made a quick ambient recording outside Mair's house to test the levels and confirm that the recorder was behaving after the drive from Manchester.

I opened that file and moved through it.

Crickets. A dog barking in the distance. A car on the B-road perhaps a quarter of a mile away.

Then the wind subsided, and there it was.

The same low tone. The same rhythm. Four seconds on, four seconds off.

I examined every night recording I had.

The tour files didn't reveal it. Those had all been made during the day, indoors or beneath the sound of crowds. But the ambient recordings captured after dark, the ones made outside once everything became quiet, all contained it.

Every single one.

Always after dark. Always when the wind fell and the background noise thinned.

I removed the headphones and placed them on the floor beside the recorder.

My neck had gone stiff. I had been sitting in the same position for perhaps an hour.

The tone was real. It existed in every quiet night file.

That meant either my equipment was detecting something consistent in the environment or there was a fault within the recorder itself. Internal noise, perhaps, or an earthing issue that appeared only in sufficiently quiet conditions.

I took out my phone and opened a new message to Imogen.

Possible audio fault in the night recordings. Low-frequency tone appearing in quiet sections. Checking whether it's equipment or environmental.

I stopped, read the message and deleted it.

It didn't sound like equipment noise. I had worked with that recorder for three years. I knew how internal interference sounded. It was generally higher, irregular and related to low battery power or temperature changes.

This signal was steady and rhythmic. It was always 37 Hz, pulsing for four seconds on and four seconds off, and it appeared only in quiet recordings made at night.

Environmental, then. Something outside was producing the tone.

Except I couldn't imagine what. Not here. Not inside the Cwm Ddu Radio Quiet Area, where the entire point was to eliminate intrusive signals.

I put down the phone and looked towards the recorder bag. The two six-packs of Panasonic batteries remained unopened in the reusable carrier beside my bed. I hadn't needed them. The original cells were still holding their charge.

Dafydd's voice returned to me.

"When it hums, don't turn towards it. Don't look for where it's coming from."

He had said it began quietly. He had believed it was the refrigerator in the forestry machinery workshop.

I picked up the phone and called Owain.

He answered after the third ring.

"Yeah?"

His voice was low and cautious.

"It's me," I said. "Have you got a minute?"

There was a pause.

"What do you need?"

I shifted on the floor and rested my back against the bed frame.

"You said there were three cases before Dafydd."

"I did."

"You know their names."

The pause was longer this time. I heard something in the background at his end, perhaps a door closing or the tailgate of his pickup being slammed.

Then Owain said, "Why are you asking?"

"Because I think I might have found something."

"Found what?"

I looked at the laptop screen. The waveform was still open, the faint thread of the tone running through it.

"I don't know yet. That's why I'm asking."

Owain Mercer said nothing for several seconds. Then he breathed out, slow and controlled.

"Are you recording this call?"

"No."

"You sure?"

"I'm sure."

Another pause.

"Then there's Iwan Griffiths. Forestry worker, fifty-two. They found him sitting upright against a tree near the Brecon Mountain Railway the previous November. No injuries. Just dead."

I said nothing.

"I waited," Owain continued. "Nia Bowen, thirty-four, pulled from the River Usk in March that year. The coroner said drowning, but she grew up beside that river. Knew how to swim. And the third was Ellis Price, seventeen. Quad-bike crash the following June. Rolled it on a trail he'd ridden a hundred times."

Three names. Three deaths.

I thought about Dafydd Morgan on the tarmac, his hand pressed to his temple, saying it gets inside.

"What connected them?" I asked.

Owain lowered his voice. "Before each one died, their families said they were hearing things. A deep humming that made them nauseous, confused, paranoid."

There it was.

I sat forward. "The same as Dafydd?"

"The same as Dafydd."

"Did anyone investigate? The humming?"

"Investigate what? No one else could hear it. Only them. Doctors put it down to stress, perhaps some early neurological problem. Then they died and it stopped mattering."

I thought about the tone in my recordings. Low, rhythmic, four seconds on and four seconds off.

"What if it wasn't only them?" I said.

Owain was silent for a long moment.

Then he said, "Don't."

"Don't what?"

"Don't dig into this. I'm serious."

"I'm only asking questions."

"Yes. And that's how it starts."

There was an edge to his voice now. Not anger. Worry.

"You think you're the first person to notice that something doesn't add up here? You're not. And the people who pushed it didn't get answers. They were told to stop looking."

"By whom?"

"Does it matter?"

"Yes," I said. "It does."

Owain exhaled again, more sharply this time.

"The Cwm Ddu Radio Quiet Area has statutory protection that goes well beyond ordinary local policing. You understand that, don't you? UKRI and STFC arrangements, observatory security, local police liaison, government contractors. People whose job is to make certain nothing interferes with the telescope. They don't like complications."

I said nothing.

Owain went on. "You're here for a job. Record your sounds. Give them to your journalist. Leave. That's all. Don't turn it into more than that."

"What if it already is?"

"Then leave faster."

I looked at the recorder, the laptop screen and the reusable carrier bag with the batteries still on the floor.

"Thanks for the names," I said.

Owain did not answer at once.

When he did, his voice was quieter and flatter. "You're not going to leave it alone, are you?"

"I don't know yet."

He made a sound that might have been a laugh, but wasn't.

"Yes, you do."

The line was silent for a second.

Then Owain said, "Be careful," and ended the call.

I lowered the phone and looked at the list I had written on the corner of a receipt.

Iwan Griffiths. Nia Bowen. Ellis Price.

Three people dead in less than a year. All of them had heard humming no one else could hear. All of them had become disorientated, nauseous and paranoid before they died.

And I had a tone in every quiet night recording I had made since arriving.

Owain's warning remained in my head.

Don't dig into this.

The sort of thing people say when they know something and do not want you to discover it. The sort of warning that makes you want to verify it for yourself, if only to find out whether they are right.

I pulled the laptop closer and opened another file. The waveform appeared across the screen, that thin thread at 37 Hz running through it.

Dafydd Morgan's inner-ear structures were gone. He had lived and worked normally for decades, yet the CT and subsequent MRI showed no trauma, no operation, no scarring, nothing to suggest they had ever been there. Three people before him had heard the same hum, and I had recorded it.

Owain was probably right. I should have packed the recorder, sent Imogen Clarke what she needed and driven back to Manchester that night.

I didn't.

I made certain Imogen's commission was complete first. I organised the daytime recordings, checked the tour audio, labelled the visitor-centre atmosphere and backed up every usable file. Only when the paid work was ready to deliver did I wait for darkness.

There was no clever reason for that. The tone only appeared clearly at night, when the countryside was quiet. If I meant to locate its source, I needed it loud enough to follow.

At 21:45, I loaded the rented estate car. Handheld recorder, spare batteries from one of the Panasonic packs I had finally opened, and my best headphones, the closed-back pair I used for field monitoring when I needed to hear every detail. I wore the same jeans and hooded top I had worn in the car park two nights earlier. The recorder bag went across my chest.

Mair Hughes's porch light was on when I pulled away, but I did not see her at the window.

The drive to Cwm Ddu took twenty minutes. There were no other cars and no lights apart from my headlamps cutting between the trees and the occasional reflector post marking a bend. The visitor centre appeared first, dark and empty, its car park completely clear.

I kept driving.

About 400 metres beyond the main entrance, the road narrowed and a sign appeared on the right.

RESTRICTED ACCESS. AUTHORISED PERSONNEL ONLY. CWM DDU RADIO QUIET AREA. GOVERNMENT RESEARCH LAND.

Another warning sign stood 15 metres farther on, its smaller print referring to statutory radio-protection powers, observatory security and enforcement.

Then came a chain-link gate roughly 2.5 metres high, secured with a sliding bolt and padlock. There was no guard and no camera I could see, although that meant very little.

I pulled on to the gravel verge about 30 metres before the gate and switched off the engine. For a moment I simply sat there, hands on the wheel, recorder bag in my lap.

This was where I should have turned round.

I got out.

I expected to find a generator. Perhaps a cooling system for some piece of equipment, something mechanical hidden away and run at night when visitors were gone. That would explain the low frequency, the regular rhythm and why it only emerged after dark, when other systems and background noise died away.

I put on the headphones, switched the recorder to standby and listened.

At first there was nothing but wind, shifting leaves and my own breath trapped inside the headphone cups.

Then I caught it.

Low. Deep enough that I felt it in my ribs before I heard it in my ears. The same tone as the files, only stronger now and no longer filtered through a recording.

It pulsed for four seconds, stopped for four, then returned.

I turned my head left. The tone faded slightly.

I turned right. It grew louder.

That was when I realised it was not coming from every direction. It had a source.

I began walking, keeping off the road and moving through the trees parallel to the fence. The hum rose and fell according to which way I faced. I used that, turning slowly with the headphones on and letting the volume guide me.

When I faced the observatory, back towards the visitor centre and the great dish of the Cwm Ddu Radio Telescope, the sound weakened.

When I turned away from the CDRT, towards the ridgeline east of the site, it peaked.

That made no sense. The entire purpose of the Radio Quiet Area was to protect the telescope from interference. If equipment was generating the signal, it ought to have been associated with the observatory itself: cooling fans, data servers, something supporting the dish.

Instead, the strongest signal was drawing me away from it.

I kept walking.

The tree line opened on to a dirt pull-in about a hundred yards from where I had parked. There were tyre tracks in the mud, recent enough that their edges remained sharp. Two sets, perhaps three. Probably a works vehicle, something with broad treads.

Beyond the pull-in, 6 metres into the clearing, stood a windowless brick-and-concrete relay bunker. It was roughly 12 feet square, with a flat roof and one metal door. A common brass Yale padlock hung through the latch. There were no signs, asset numbers or markings to show what it contained or who had built it.

For a moment I felt a peculiar relief. Padlocks meant people. Human infrastructure, human rules, something I could understand even if I was not meant to be there.

I stood at the edge of the clearing and stared.

The hum was louder now. Loud enough that I pulled the headphones down around my neck. I did not need them any more. I could feel the vibration in my chest, my throat and the space behind my eyes.

I should leave.

The thought was clear, practical and obvious.

I stepped towards the bunker.

The hum surged.

Not gradually. It jumped, as though something inside had noticed me or changed modes. My stomach rolled so violently that I stopped and pressed one hand against a tree to steady myself.

I closed my eyes, breathed through my nose and told myself it was only infrasound, low enough to cause nausea. Nothing supernatural. Nothing more than physics.

But beneath the hum, barely audible, I caught something else. Thin, sharp clicking, rapid and rhythmic. Almost mechanical, but not random. It had structure. Patterns like Morse code, perhaps, or a data transmission shaped almost like speech.

I opened my eyes.

The Yale padlock was ordinary, the sort anyone might put on a garden shed. Bolt croppers would have cut it. A hard pull with a crowbar might have torn the latch screws straight from the frame.

I was not going to do that. Perhaps breaking a government padlock felt different from trespassing on restricted research land. Perhaps I still wanted to believe I had not crossed that line.

Instead, I circled the bunker.

A vent about 15 centimetres square had been fitted low in the back wall and covered with a metal grille. There were no visible screws. The grille seemed to be pressure-fitted into the concrete surround.

I knelt.

The hum was strongest there. So was the clicking. I could hear it clearly now, layered beneath the low tone. The individual clicks came quickly enough to blur, but not so quickly that they seemed continuous.

They pulsed, stopped for four seconds, then began again.

I slipped the recorder from my shoulder, pressed record and checked the levels. They leapt into the red, dropped, then spiked again in time with the hum.

I lay on my side in the dirt, stretched out my arm and pushed the recorder as close to the vent as I could.

The levels rose.

Whatever was inside was not random. It repeated: the same pulse, the same rhythm, the same clicking pattern buried beneath it.

Not a generator. Not a cooling fan.

A message.

A light came on inside the bunker.

I was still lying in the dirt, recorder extended towards the vent, when the glow spilled through the grille and struck my hand. Sickly yellow fluorescent light, the sort that buzzes in empty offices.

I did not move.

I should have moved. My mind told me to get up, pull back, run. My body remained frozen, arm outstretched, the recorder barely 15 centimetres from the vent.

The hum did not change. The clicking continued in the same pattern beneath it.

Then I heard the padlock.

Not someone handling it outside. The sound came from within: a clean, deliberate metallic click, followed by the bolt sliding free.

The door swung outwards.

I snatched back my arm, scraping my elbow against the concrete, and rolled on to my knees. The recorder remained in my hand. I do not know why I did not drop it.

A man stepped out.

He did not hurry. He moved like someone checking the weather. Boots first, then the rest of him. He stopped outside the doorway with one hand resting on the frame.

He wore a headtorch. Its beam swept the clearing in a slow arc from left to right, as though he were listening more than looking. His green jacket bore a shoulder patch I recognised from the visitor centre: the observatory contractor's emblem, the same logo and lettering.

His name was Malcolm Veysey. I did not know that then. I learnt it later.

He turned his head and the beam struck me full in the face. I could see nothing beyond the white light and the after-image of trees.

"This area is restricted," he said.

His voice was calm. Not loud or angry. He was simply stating a fact.

I stood. My legs felt wrong. The hum continued and my stomach rolled again, but I locked my knees and remained upright.

"I didn't see a sign," I said.

It was a stupid lie. I had driven past two.

He did not answer immediately. He tilted his head and the light descended from my eyes to my chest, then to the recorder bag and the unit still in my hand, its red recording lamp illuminated.

"Recording equipment makes it worse," he said.

I pressed stop. My thumb found the button through muscle memory and the red light went out.

"I'm working," I said. "I'm doing a job for a science journalist. Recording ambient sound. I heard something out here and wanted to check whether it was an interference problem."

He watched me. The headtorch kept his face invisible, but I could feel his attention fixed on me.

"You're not the first person to follow the hum," he said.

My chest tightened.

"I don't know what you mean."

"Yes," he said. "You do."

He stepped aside and lifted one hand. It was not pointed at me. It was a signal.

Two more lights came on among the trees behind me.

I turned. I could not help it.

Two people stood about 10 metres away, positioned to block the route I had taken into the clearing. One to the left, one to the right. Both wore the same green jackets and headtorches.

I looked back at Malcolm. He had not moved.

"We're going to need the recorder," he said.

"It's my equipment."

"I know."

"I need it for work."

"You can buy another."

I did not hand it over. I knew I should, but I held on to it.

Malcolm sighed. Not with frustration. Only weariness.

"This is easier if you cooperate," he said.

The other two began to approach. They did not rush. They merely closed the distance.

"All right," I said. "I'll go. I'll leave and I won't come back."

"Yes," Malcolm said. "You will."

That stopped me.

"What?"

"You'll leave tonight. Tomorrow you'll think about it. The day after that, you'll start looking for another way in. That's how it works."

The others were 3 metres away now, close enough for me to see them properly. The one on the left was a woman in her late thirties, perhaps, her hair pulled tightly back. The man on the right was taller and solidly built.

Both looked at Malcolm, not at me.

"Inside," Malcolm said.

"I'm not going in there."

"You are. You can walk, or Glyn can help you. Your choice."

Glyn Harper, the tall man, said nothing. He did not need to.

I walked.

Malcolm stepped aside and I passed through the door into the bunker.

It was hot inside. Not warm. Hot with the stored heat of electronics running too long without proper ventilation. The air smelt of metal, ozone and something sharper that I could not place. Burnt plastic, perhaps.

The room looked smaller from within. Roughly 12 feet square, but the racks along the walls made it feel tighter. Black metal equipment frames had been bolted to the concrete and filled with units I did not recognise. No manufacturer's marks, only smooth black cases, ventilation slots and a scattering of blinking LEDs.

In the centre stood a chair bolted to the floor, facing a black panel on the far wall.

The hum was worse in there. Not louder, exactly, but more physical. It vibrated in my jaw and teeth and behind my eyes.

Malcolm entered behind me, followed by the woman and Glyn. The door remained open, but Glyn stood across it.

"Sit down," Malcolm said.

I looked at the chair. It was only a chair: metal frame, flat seat, no arms. But it was fixed to the floor, and that made it something else.

"I don't want to."

"I know," Malcolm said.

I sat.

The woman moved to one of the racks and removed a small black sensor from a hook. A wire trailed from it. She clipped it to my collar without speaking, her hands quick and precise.

She did not look at my face.

The panel in front of me flickered. It did not quite switch on. It merely flickered as though waking, then began to pulse.

Four seconds on. Four seconds off.

The rhythm from the recordings.

But it was not sound. It was light, or something close to light. It illuminated nothing. It simply was.

My vision stuttered.

The room was there, then it was not, then it returned displaced slightly to the left. My balance lurched sideways and I gripped the edge of the seat.

"Relax," Malcolm said.

I could not. My inner ear insisted I was falling although I sat perfectly still.

The woman watched a small display mounted in the rack. I could not see what it showed.

"Elevated," she said.

Her voice was flat and clinical.

Malcolm nodded. The pulses continued.

My stomach rolled and bile rose into the back of my throat.

"What are you doing?" I asked.

"Compliance monitoring," Malcolm said. "Quiet Area enforcement."

"This isn't enforcement."

"It is now."

Another pulse. My vision stuttered again, and pressure began to build in my left ear. Not pain. Pressure, like descending too quickly in an aircraft.

Then I saw the camera, small and mounted in a corner near the ceiling, with a tiny red light beneath its lens. On the side of one equipment rack were a Met Office asset label and a UKRI equipment mark.

They gave me a stupid flicker of hope. Oversight. Paperwork. Procedures. Not violence.

Malcolm saw where I was looking.

"Some people can't help it," he said. "They hear the signal and they have to follow it. Like you."

"I'm only doing my job."

"No. You finished your job two days ago. You're here because you couldn't stop."

He was wrong about the timing, but not about the rest. The commission had been completed before I came out there. I had no professional reason to be in that bunker.

The woman checked the display again.

"Rising," she said.

The pulses seemed to accelerate, not in rhythm but in their effect on me. Each four-second flare stretched across my vision. Each four-second darkness felt shorter than the one before. I could no longer tell which way was up.

I bent forward until my hands struck my knees and concentrated on that solid, real resistance.

"That makes it worse," Malcolm said. "If you keep analysing it, you risk lasting harm. Stop trying to understand it. Let it pass."

I did not know how to stop analysing. That was the whole problem.

But I tried.

I released my knees. I sat back. I stopped attempting to count or track the pulses and let them happen.

They did not stop, but something changed. The pressure in my left ear levelled out. The nausea remained, but ceased to climb.

The woman said something I did not catch.

The panel went dark.

She unclipped the sensor from my collar, her hands again quick and impersonal.

Malcolm stepped back.

"You can go," he said.

I stood too quickly and the room tilted. I caught the back of the chair and waited for it to right itself.

"Slowly," Malcolm said.

I moved slowly, one step and then another. Glyn shifted away from the doorway and I walked into the clearing.

The air outside was cold and clean. I dragged it into my lungs as if I had been underwater.

"Leave Powys," Malcolm said behind me. "Don't come back. Don't talk about this."

I did not answer. I walked.

I reached the trees before I had to stop and brace myself against a trunk. My legs were shaking. The hum remained, but it was quieter. Or perhaps I was simply farther from the bunker.

I could not tell.

I kept moving.

Owain found me beside the estate car. I do not know what time it was. Late or early. The sky had taken on the pale edge that comes before dawn.

I was on my knees beside the rear bumper, one hand gripping it, my stomach empty. I had been sick twice, perhaps three times. I had lost count.

Owain's truck pulled up behind me. Its headlamps flooded the gravel, stretching my shadow long and thin in front of me.

He got out. I heard the door and then his boots on the ground.

"Christ," he said.

I did not look up. He crouched beside me.

"Can you stand?"

"Yes."

I couldn't.

He put an arm beneath mine and hauled me upright. I leant on him harder than I intended.

"What happened?" he asked.

"I went to the bunker."

He did not ask which bunker. He only swore under his breath and opened the passenger door of his truck.

"Get in."

I climbed in. He closed the door and went back to my estate car.

I watched him in the side mirror. As an on-call community responder who also handled occasional maintenance liaison for the observatory, he knew the local sites, the contractors and too much of what happened after hours. That was how he had known where to find me.

He reached through the driver's window, released the boot and retrieved my recorder bag. It had been accessible where I had left it amongst my kit. He carried it to the truck and placed it on the back seat.

Then he drove.

We did not speak. I kept my eyes closed and concentrated on breathing. The road was rough, and every bump turned my stomach, but there was nothing left to bring up.

When the truck stopped, I opened my eyes.

Mair's house. The porch light was still on.

"Go inside and pack," Owain said. "Now. Everything. Don't leave anything behind."

"I need to sleep."

"You need to leave. If you're still here in two hours, they'll come back."

I believed him.

I got out. My legs barely held me.

Owain stayed in the truck with the engine running while I went inside. Mair was not in the kitchen. I did not see her.

Upstairs, I packed everything into my holdall and rucksack. Clothes, cables, batteries and the unopened bottle of sparkling water I had bought at Home Bargains before Dafydd collapsed. It had remained with my belongings after the ambulance took him away.

Packing took perhaps ten minutes.

When I came downstairs, Owain stood beside his truck.

"Straight to Manchester," he said. "Don't stop except for petrol. Don't come back."

"All right."

He studied me for a long moment.

"I'm sorry," he said.

"For what?"

"For not lying better when you asked about Dafydd."

He climbed into his truck and drove away.

I put my belongings in the estate car, placed the recorder bag on the passenger seat and started driving.

I checked the recorder an hour after leaving the area. I pulled into a petrol station, bought a service-station coffee I did not drink and sat in the car park with the unit on my lap.

I scrolled through the files.

The recording from outside the bunker was gone. Not merely deleted but wiped clean. Its slot was empty, as if the recording had never existed.

I checked the others.

The daytime material remained: tours, ambience, the visitor centre, all intact. Only the night recordings had vanished. Every one of them.

I sat staring at the empty list for perhaps five minutes.

Then I returned the recorder to its bag and drove on.

Two hours later, my left ear began to bleed.

I noticed the warmth on my neck first and wiped it with my hand. The blood was bright red. I pulled over and checked the rear-view mirror.

It was coming from inside the ear. Not much, only a slow trickle. I pressed a paper serviette from the petrol station against it and waited.

It did not clot. It slowed, but it did not stop.

My hearing on that side became dull. Not absent, only muffled, as though someone had packed cotton wool deep into the canal.

Beneath that muffled silence was constant pressure. The same pressure I had felt in the bunker.

I kept driving.

I delivered Imogen Clarke's commission three days after I returned to my Manchester flat. Tours, ambience and visitor-centre atmosphere. Clean, usable daytime files.

She paid the remaining fee on delivery. I needed the pounds, and failing to deliver after completing the assignment would have raised questions I did not want to answer.

She asked whether I had captured anything unusual.

I said no.

She told me the material was solid and that she would ring when she had another job.

I said, "Sure."

After that, I stopped wearing headphones for long sessions. An hour, perhaps two, and then I had to take them off.

Close listening triggered something. A tightness in my chest. A low hum at the edge of my hearing that might have been real or might have existed only inside my head.

I could no longer tell.

In quiet rooms I kept hearing it. The pulsing tone. The same rhythm.

Four seconds on. Four seconds off.

I would sit in my Manchester flat at night with the windows closed and the street noise gone, and there it would be: low, deep, just at the edge of perception.

I would go outside and it would stop. I would return and it would begin again.

Or I would hear it outside, go indoors and lose it.

I did not know whether it was in the air or in my damaged ear. Whether it was a real signal bleeding through from somewhere I could not see, a neurological injury, or something trapped inside my own head.

I knew only that I could not stop hearing it.

And I did not know whether that meant I was still listening, or whether I was already lost.