Jan Vettergren stopped typing, looked up from his laptop and sniffed the air. The smell was back, boiled cabbage and fish. This was what you got with old buildings, little quirks and peculiarities. Jan guessed the woodwork had somehow absorbed the odours of the meals that had been cooked there over the years. There were no private apartments in the neighbourhood any more, and no restaurants: nothing else to explain the smell.

He went back to work, trying to concentrate on the press release he was writing. The client was expecting it in the morning. He would have to stay till it was done, but his mind kept drifting back to what the place must have been like once. He loved the way the floorboards had been worn down in the middle of the stairs, the creaking doors, the panelled windows, bowing in their frames. And to think that it was all his.

He had thought it was a joke when they told him the price. It was all he could do to keep a straight face as he asked for a discount. The owner had given in surprisingly fast, letting Jan have the whole building for next to nothing.

People lacked imagination; that was why no one else wanted it. They couldn’t see past the tarnished walls, the graffiti and the windows on the ground floor, boarded up with perforated steel.

Jan had no problem with any of that. As soon as his fledgling PR agency had made enough money, he was going to fix up the other offices in the building and rent them out, make a fortune. In fact, he might give up PR altogether and branch off into property. Who knew how many buildings like this one were standing empty across central Copenhagen?

Jan reckoned the former owner would kick himself when he realised what he had thrown away.

They had chosen the best office for themselves, the fifth floor with the lovely original tiled stoves and the views over the red rooftops and golden church spires of old Copenhagen. One weekend, they had painted layer upon layer of pure white over the soiled wallpaper, and scrubbed and varnished the floors. The dark woods set off their modern furniture beautifully.

It was obvious no one had used the office for years. In what used to be the lounge, they had found a newspaper from 1989 tucked behind a telex machine, a beige monstrosity the size of a small fridge. On a desk, among faded carbon copies of final demands, a once-white telephone had aged to ivory, its receiver suspended in mid-air.

Strange that the previous tenants hadn’t bothered tidying up after themselves, or taken their office furniture away and sold it. Jan reckoned they must have had to close down in a hurry: bankruptcy, perhaps, or a court case.

There was no trace of the mess now. Just the little things that made Jan and his colleagues frown. Like the cooking smells. Or the sudden and inexplicable draughts. Or the fact that the white paint persisted in coming off the walls in long jagged flakes, revealing the grimy wallpaper beneath.

Quirks, that was all it was, idiosyncrasies, the sort of character people were willing to pay good money for. Jan had told the company accountant as much, but Margit was not convinced. She had worked up some crackpot theory that ‘something or someone’ was intent on expelling them. Like the Monday morning recently when they had come in to find that an unpleasant dark stain, removed from the reception floor on the Friday, had reappeared. Or when their newly mounted modern paintings had come off the walls during the night, each and every wire snapped.

None of the others had wanted to work alone in the office after that.

‘We’re not wanted here,’ Margit had said.

The thought of the melodramatic expression on her face when she said that made him laugh out loud, but his voice rang strangely in the empty room, and there was something else now, something that made him stop and listen. He closed his eyes, tried to filter out the hum from his laptop and the night buses spraying slush on the main road.

There was definitely something there, little regular creaks in the corridor. His mind raced through the options: one of his staff had come back for something, a cat had found its way in, or the central heating was making the floorboards expand and crack.

‘Hello?’ he shouted. ‘Anyone there?’

Nothing.

There was another possibility, of course: squatters. It made sense, a property standing empty for so long in a prime neighbourhood. As he strained to hear, he made a mental note to call in a security firm in the morning.

The little creaks started up again, louder this time. They sounded a lot like footsteps now. He looked around for a weapon, picked up an umbrella and put it down again. Considered a cardboard tube holding proofs of new posters for Copenhagen’s City Bikes, but thought better of it. Finally, he settled on a magnum of champagne someone had brought to their launch party. He held it like a club.

The corridor was empty. Where the white paint had come off in scrolls, you could see pale ovals and rectangles on the old wallpaper, the shapes of pictures that had once hung there.

The meeting room was deserted and dark, the plasma screen for their video conferences still in its box and stacked against one wall. After the incident with the paintings, no one had felt much like trying to mount it. Jan told himself that once he had investigated the strange noise, he would unpack the screen and hang it, using the power drill and four-inch bolts he had brought from home.

In his partner’s office, there was still a sheet draped over the desk, though they had managed to clean up most of the mess. It was unfortunate what had happened to Kristoffer. They still had no idea how the screws holding the heavy ceiling lamp directly above his chair had managed to work themselves free from the plaster. Bad luck that he had been sitting there at the time.

Jan looked inside the galley kitchen where they kept their Italian coffee machine and the microwave and their personal mugs, all eight of them lined up on the counter. Jan doubted Kristoffer would have much use of his now.

The kitchen was cold, though the window was closed. The smell of cabbage and fish was stronger here. Perhaps there was something rotten in the bin? He was about to open the lid and have a look inside when he was startled by the lift starting up, pulling noisily on its cables in the shaft on the other side of the wall.

He was the only one who used the ancient contraption. The others were put off by its narrow dimensions and the way it sometimes ran by itself or stalled on their floor, endlessly opening and closing the doors on the empty car. The date of the last service was 16 October 1991, according to the signed engineer’s report fixed to the wall inside.

Jan went out on the landing and looked at the old-fashioned half-moon display above the lift. The car had descended all the way to the cellar. He reached out for the call button, but changed his mind and turned towards the stairs, lest he gave himself away to the intruder.

The stairwell was shabby and poorly lit with a faint, bittersweet smell of Bakelite and cigars. Light rectangles on the linoleum showed where there had once been doormats at the entrance to each apartment. Signs announced the names of businesses long gone: an independent record label, a reflexologist, a temping agency. One door was blackened by soot, and another had been gutted by what looked like an axe, leaving the wood in long, jagged splinters.

Jan bent down and looked through the gap. On the hallway floor inside lay a pile of unopened mail. The envelopes looked green and fuzzy, as though made from felt or some organic material. He recoiled as he realised they were covered in mould. A trail of dark stains led off into the murky depths of the apartment.

He continued down the stairs, almost stumbling in fright when his phone went off in his pocket. It was Margit.

‘What is it?’ he snapped, annoyed with himself for being so jittery.

‘Where are you?’

‘At work, someone has to be.’

‘If I were you, I’d leave at once,’ she said. ‘I’ve done some research. There was this tenant once, back when they turned the block into offices. They say that he refused to leave.’

‘Blah, blah, blah,’ Jan said. ‘I’m not listening.’

He walked over to the window. Across the snow-speckled courtyard he could see the larger and more imposing office building that fronted the road. It had been refurbished a few years ago, the old features ripped out and replaced by New York loft-style bricks and beams. The open-plan floors were lit up, showing row upon row of white desks and chairs.

It was strange to think that where suited advertising executives now spent their days sipping cappuccinos, hundreds of men, women and children had once lived together, crammed into tiny apartments, with a shared outside privy. Must have been freezing in winter, Jan thought.

Margit was still talking when he put the phone back to his ear: ‘Kristoffer may never be able to return to work. It took them the best part of a day to remove the shards of glass from his scalp and face.’

Jan had heard enough. ‘Margit, if you want to keep working for me, I suggest you forget this superstitious nonsense. I’m hanging up now.’

‘Wait, where are you exactly? What’s that echo?’ he heard Margit say before he ended the call and continued down the stairs.

Nothing happened when he flicked the light switch to the cellar. He hesitated on the steps, weary of the dark. Years ago, people would have done their laundry down there in great steaming vats, pegging their sheets on lines strung across the courtyard. There was a smell of wet cement. Somewhere in the darkness below, a tap was dripping.

He held up his phone and descended the steps very slowly, struggling to see in the foggy blue light from the display. Towards the back of the cellar, there was a row of lock-up storage rooms, one for each of the twelve apartments. He pointed the light through the grilles, saw a rusty bicycle, stacks of wooden crates, an old pram.

His grip tightened around the neck of the champagne bottle as he reached the lock-up belonging to their office. Slowly he lifted his phone and shone the light inside. Nothing, just stacks of old newspapers, discarded lamp-shades, a mattress and bits of worn carpet.

It took a while for his heartbeat to return to normal. Then he got angry. Someone had deliberately sent him on a wild goose chase to the cellar. He had thought himself on an intruder’s tail, when all along they had only wanted him out of the way so they could clear out the office computers and TV screens.

He raced up the stairs two steps at a time, but he was too late, someone had been in his office already. The papers on his desk had been knocked to the floor and were fluttering all over the place.

‘Show yourself, whoever you are!’ he shouted.

One of the windows had been opened, filling the room with icy, wet air. The pane kept slamming back against the frame, like someone knocking urgently on a door. Jan remembered that there was a narrow ledge outside the window, big enough to hold a man. He pretended to leave the room, deliberately making a loud noise as he did so and switching off the light.

‘Don’t make me come and find you,’ he shouted down the hall.

Then he tiptoed back into the room, the bottle of champagne raised high above his head. No one was going to put Jan Vettergren off; no one was going to stop him from doing exactly as he pleased with a property that was his by rights.

Perplexingly, the ledge was empty. At least he thought it was. He had to climb out of the window completely before he could be certain.

The bottle fell first. There was a long silence before it smashed on the cobbles in the yard far below. With an instinctive reaction, Jan leant forward to catch it, his hand grabbing fistfuls of air.

There was a brief moment before he lost his fight against the greater force pushing him forward, a split second in which he saw exactly what would happen: they would find him on the cobbles in the morning, surrounded by glass from the broken champagne bottle. It would look like an accident, like high jinks gone disastrously wrong.

No one would listen to Margit, a middle-aged bean counter with an overactive imagination. With neither Kristoffer nor himself around to run things, the lawyers would wind up the PR company and, eventually, the property would change hands again, as yet another buyer with a keen eye for a bargain succumbed to its charms: Unique historic property in the heart of Copenhagen, bags of potential, a diamond in the rough.

At the time it had not seemed important, but Jan recalled now how vigorously the previous owner had shaken his hand, how quickly he had headed for the door.

As the ground rushed towards him, he could hear the window high above slamming and opening, slamming and opening, like cruel, slow-handed applause.