Although theoretically the magazine's office is open until 5pm, no-one works until then on Fridays. But someone has to answer the phone and emails during office hours, and this week it was my turn. My turn comes round a lot, but that's because I'm still the new girl, and not seen as a proper journo.

People drifted away from lunchtime onwards, and I tried to find something to do – everything I'd had to complete for the next issue was filed and with the editors; I pushed back my chair and let my mind wander lazily (Someone'd turned the heating up this week and it made me drowsy in the afternoons.)

The deputy editor was the last to leave, about four o'clock. Apart from maybe Brian in the basement. It was dark and drizzling outside, the lights were mostly off, and the final hour stretched ahead interminably. "See you in the pub, Georgia?"

Some of the others were meeting for a drink, to avoid obnoxious little trick-or-treaters; it sounded a sensible plan, and I'd said I'd join them. Some were making a night of it, dressing up and that, but I was going straight from work: my only concession to the season being red/black stripey tights (the nearest I have to anything witchy), with black ankle boots, a burgundy top and cute but work-safe black miniskirt. "Sure. If I survive this last hour."

*

Left alone, my thoughts drifted to the Church Durton weirdness the previous weekend. At the time it had been very unsettling, but from the distance of a few days I'd begun to wonder whether I hadn't overreacted a bit. OK: there was a cloudy, vaguely nun-shaped anomaly on my accidental photos (and the party photos were all fine, so it wasn't smut on the lens); my companion, Sarah, had been very shaken ("s****ing f***ed-up", were her exact words on it); and that groaning sound had really gone through me and made my skin crawl (just as much as it'd freaked out Sarah). I also didn't like the way it'd all happened just hours after the surreal conversation with the little grey librarian about that odd book. But I didn't see it was anything for me to continue to worry about.

Yet, I'd been unable not to.

I realised we might have something on Church Durton in the archive – it's the kind of place we'd feature for all sorts of reasons. I shut down, set the answerphone, and made my way to the basement.

I'd only been down once before, on my new-start's tour of the place, so I was unprepared for the drop in temperature, compared with the office. "Brian?" No answer from the dimly-lit space, though there was some shuffling in a back corner. The basement of the building was old cellars from when it had been a nice Victorian townhouse – but the brick vaulting made them dark and awkward. Brian was a retired photo editor, who had chosen to spend his twilight years sorting out what we grandly called our archive. He was usually grumpy, but good at his unofficial job. "It's Georgia. The new photographer? I need to look something up, but I'm just going to fetch my cardigan – it's cold down here."

On the way back down from grabbing my thick cardigan from my chair, I bumped into Brian coming out of the ground-floor kitchen. "Hello. Still here?" He always smiled when we crossed paths, as he had a soft spot for photographers.

"I'm on the phones, but I wanted to look something up. Did you hear me call out down there? I didn't realise how cold that basement is, so I came back for my cardie."

"Got used to it, me." He led me down the stairs. "I didn't hear you, been up here for the last ten minutes. Some scruffy sod left a pile of dirty mugs."

I shrugged, certain I'd heard someone.

When I told Brian what I was after (carefully making it vague) he showed me various places in the maze of cupboards, filing cabinets, shelves and little nooks and corners. "I'm off any time now, Georgia, so if you want to stay, just leave everything on the desk, and I'll sort it on Monday. Oh, and lock the door." He handed me a key, which I slipped into my cardigan pocket.

Why wouldn't I want to stay?, I wondered. "Cheers, Brian. See you."

In one of the files was a long article from years back about how the Church Durton house had been built on the site of a medieval convent: with pictures of the same corridor Sarah and I'd been wandering about on, incorporating the old cloisters. I shivered, remembering the otherwordly moaning we'd heard.

I jumped when there was a clatter to my left. A drawer in one of the cabinets had slid open. Still reading the article, I went and shoved it closed with my hip.

Another clatter. I looked up to see a drawer on the opposite cabinet had done the same. The floor was uneven, so they probably did this a lot, I thought, moving round some heavy wooden boxes of photographic slides to shove that one closed too. The first one sprang back open – actually sprang (I happened to be glancing at it) – and I felt a tickle on the back of my neck like the crawling sensation at the Old Priory. As I went to shove that drawer back, all the drawers in both cabinets flew open and the lightbulb behind me fizzled and went out.

I banged my knee on the pile of boxes. "Ouch. Bugger."

I thought I heard a stifled giggle from a nook further behind me, but when I whipped round the lightbulb popped back into life. There was no-one, obviously.

I rubbed my knee, then my neck (hoping to get rid of the goosebumps). "Brian? You still there?" No answer.

The first drawer banged itself shut as I moved towards it, and for a moment I stood stock still. I'm a reasonably practical girl, fairly rational, and I'd always thought I wouldn't know a ghost even if one bit me on the nose.

As soon as I'd had that thought, I actually felt my nose twitch like someone had tweaked it. Like boys used to, in the playground when we were seven. I sneezed, and heard the ghostly giggle again. "Don't be stupid," I said aloud, but I didn't feel confident and wasn't sure I wasn't talking to myself. But why should I suddenly leap to the whole "ghosts" conclusion?

There was another snigger, and maybe a scuffling, and the lightbulb fizzed for a second then popped.

And stayed on.

I let my breath out heavily. Putting the article on the boxes, I stepped carefully round the cabinets and into a part with high wooden shelves. No-one. No-one in the next bit either, which was the end of the basement.

As I returned, I felt a draught of really chilly air lift my hair. I tugged my cardigan tighter. Then an entire shelf-load of box files tumbled one-by-one off the racking in front of me, like a domino trick. It was beautiful to watch, in a way, but the contents scattered at my feet, and I definitely heard a laugh.

This wasn't a snigger, it had a gleefully mischievous edge.

"Who are you?", I blurted out inadvertently.

Something whispered, Harriet.

I think.

"Well. Listen up, Harriet," I said, more firmly than I expected. "I'm leaving you to your antics and going to the pub. Night night." Striding swiftly to the door, I pulled it shut behind me, took the stairs two at a time, grabbed my stuff, and got the hell out of the office. I desperately resisted the temptation to look over my shoulder, and was shaking so much I could barely set the intruder alarm.

The pub was cosy, the others were fun. I got tipsy and went home feeling much better.

*

On Monday, I took the basement key (which I'd found in my pocket) down to Brian, hoping he wouldn't mind I'd forgotten to lock the door. Or left a huge mess. "Brian, I'm so sorry. I forgot to lock the door..."

"Worse than normal, this," he grumbled from amongst the strewn papers.

I feigned ignorance, glancing around anyway (despite myself). Nothing, of course. "What's happened?"

He pointed upwards. "Draught from that bloody old grate. Covered it over years ago, but still...."

I gave him a hand, keeping my mouth shut.

Back at my desk, there was an old issue of the magazine on it, from the 1950s. No-one knew why it might be there. When I turned back to look at it, it ruffled quickly open to an article about the history of the building when it had been a house. My neck prickled again, and when I spotted the name Harriet on the second page, I knew I would be spending the morning reading...