On first viewing the two-storey semi-detached on Lansing Close, Helen Rutledge dismissed outright the absurd but overpowering impression that she was not welcome here. She was a sensible young woman – all right, no longer all that young – who routinely privileged the should over the was. This should be the perfect house for her; ergo, it was. Three bedrooms, for herself, a study (perhaps in time a nursery?) and guests: tick. Not one of those decrepit Georgian headaches whose renovations were hogtied by preservation orders, the structure was at least postwar: tick. Granted, the nondescript semi of yellow brick was located in deep south London, but any property whose purchase someone in Helen's income bracket could swing was bound to involve a hefty commute to a job in NW1. Indeed, that was the clincher: the house was a steal. Tick, tick, tick!

As for whether she harboured any reservations about 21 Lansing Close having been repossessed, the answer was certainly not. A tax accountant, Helen held rules in high esteem, second only to those who followed them. She had no sympathy for people who didn't exert control over their circumstances – who allowed their lives to go all higgledy-piggledy and so created messes for responsible citizenry to clean up. For Helen, the prospect of being unable to pay any bill slipped through her letterbox was mortifying. If the previous owner had purchased a property beyond his or her means, such culpable foolhardiness ought rightly to be punished, and that's all there was to it.

Given the paltry asking price, or paltry in London terms, she was surprised to face no competition, and the estate agent acting for the bank accepted her offer with a hastiness that more seasoned house hunters might have found alarming. But as a first-time buyer, Helen wasn't about to look a gift house in the mouth. She would continue to rent her flat in Dulwich for a month after completion in order to do a spot of sprucing up. The persistent unpleasantness that imbued the interior – nothing that you could put your finger on, nothing that you could explain, and therefore nothing – could surely be ameliorated with a few licks of paint.

Handy for her gender and generation, Helen spent her first Saturday as a landholder covering the sitting room walls in a vibrant, nervy colour that she'd found in the Guardian Weekend's interior design pages: a dazzling aqua popular for plastic toys. By late afternoon, a beaming second coat had obliterated the sombre underlying shade, a light grey with a queasy purple undertone, as if the room had been bruised. Even if the new paint job hadn't, somehow, settled – the panels of blue-green seemed to float slightly forward of the plasterboard – she'd introduced a splash of vivacity to the ground floor.

She returned the following morning to have a go at the skirting boards. Yet her key simply would not turn the upper lock, though she jiggled it this way and that for a solid 10 minutes. Whoosh up the homeowner's learning curve: when it was your property, you couldn't ring the landlord to come and fix it, and Helen fought an urge to cry. The house didn't like her and didn't want her inside.

The sensation of personal rejection being flagrantly ridiculous, she got a grip and located a locksmith on her mobile, then sat on the step to wait. It was autumn, and she noticed too late that a scraggly tree growing at a deranged angle overhead had dropped stinky violet berries on to the step. The seat stained with purple blotches that would never wash out, now her jeans looked bruised as well. Worse, once the locksmith rocked up, he tried the key once and the door swung wide, open sesame. He still charged a call-out fee, quite a packet to part with for the privilege of feeling like a dunce.

In the entryway, the quality of the light glooming from the sitting room doorway was inexplicably dingy and sulking, when the south-facing front windows still had no curtains and the weather was fair. Helen ventured in to admire yesterday's daring makeover, only to find the walls a colour that would never be employed for a toy. The shade was still blue, of a sort, but sullen. Rather than refract the sunshine shafting through the windows, this hue consumed the light, sucking every photon thirstily from the rays like a child slurping the last of a soda. When she came closer, it was clear the paint hadn't dried to speak of, either, or just enough to have grown mucky and thick. The surface was bubbling as well, making creepy little pipping sounds, and in long vertical streaks the old purplish grey glowered through. Since obviously the whole job would have to be done again, she touched the paint that had looked so jaunty and dashingly modern when she locked up on Saturday, and it stuck to her finger, stringing like bubblegum when she pulled away. There was simply too much of this guck, too, as if the outrageously defective product that she'd slathered on her sitting room was actually dissolving earlier layers of paint beneath.

Which was the only explanation for what rapidly emerged on the far wall. At first she thought it was a trick of the queer light, or an accidental arrangement of streaks and blisters. But no, those were letters – in black, crudely formed and dripping, as if slashed with a wide, over-laden brush, and underscored for good measure:

MY HOUSE!

So spiteful were some delinquent homeowners, it was said, that they vandalised their own homes before being evicted. The bank would have arranged for any damage to be tidied before putting the house on the market. And now her warped poor luck with a bad batch of paint – she might as well have covered the room in battery acid – had exposed some ghastly deadbeat's defiant parting graffiti.

"It's not your house any more!" Helen announced aloud – though the walls ate the sound as voraciously as the light, and her voice sounded terribly tiny.

She returned the remains of the paint in a state of righteous indignation, but the salesman at B&Q was sceptical – even more so once she'd described the burbling horror show in gory detail. "Never heard of that, love. Sure you didn't just apply the second coat before the first was dry?"

"If I can execute the directions in 11,520 pages of Her Majesty's tax code," she huffed, "I can follow the back of a tin." But he clearly delivered her refund only to get this incompetent crackpot out of his hair.

By the time she stopped back by Lansing Close midweek, it was evident that the paint would never cure. The sticky mess couldn't be called "Island Breeze" now, for it had churned into a vomitty miasma of a colour so ambiguous that it wouldn't have a name. So Helen was obliged to hire a contractor to replace the plasterboard. When it came time to choose a colour for the sitting room again, she found she'd lost her nerve, and opted for an innocuous hue the contractor recommended called "Moonlit Sky", which turned out to be light grey with a queasy purple undertone.

For her second home-improvement project, Helen fancied ripping up the nubbled carpet of a bland beige in what would be her bedroom and refinishing the floorboards. All the magazines indicated that carpet was naff, and chic Londoners now opted for burnished wood accented with arty throw rugs.

But even tearing up the old wall-to-wall was exhausting. The carpet had been fanatically tacked, and the nails pierced her work gloves until her hands were sore and swollen. Slicing the carpet into the short widths that the council required for pickup entailed more than one slip with the box cutter. The nicks made her hands more painful still, so slowing her typing of spreadsheets at work that her colleague at the next desk needled her for regression to hunt-and-peck.

Once she rented the sander, the real frustration began. She knew you had to remove any nails from the flooring, and numerous tacks had pulled through the carpet and remained behind in the wood. So she had fanatically smoothed her puffy bare hands over the boards to search out even the smallest bit of metal, countersinking stray spikes with a hammer and using pliers to tug out the tacks with heads. Yet whenever she started the machine – a deafening, unwieldy monster that was honestly rather frightening – it shrieked immediately on a raised nail, which shredded the sandpaper. The belts were pricey as well as bothersome to replace, and by the day's end she must have gone through a dozen – even after repeatedly caressing the whole floor on her hands and knees, checking every square inch for extrusions.

That night, at her wit's end and having ruined yet another sandpaper belt within 60 seconds, Helen Rutledge drew the kind of conclusion that the more collected rendition of her character would have found an anathema: the floor was obviously growing nails. It was growing nails as surely as her fingers did. As a demented experiment, she meticulously traced a little patch at one corner, then turned her back. By now, she wasn't even surprised: when she returned to the patch, it sported six or seven fierce, snag-headed tacks a good quarter-inch high, which had popped up like toadstools.

"Have it your way, then," she told the floor. Sanded fitfully in small, disconnected sections, the surface had a mangy quality, like diseased urban foxes. So she was at a loss to comprehend how it still managed to look smug.

When choosing a replacement carpet, she erred on the side of caution, selecting a sample of nubbled beige. The whole tedious operation dispatched, the bedroom looked exactly the same. So far, after much expense and effort, Helen the new homeowner had made no impact on this property whatsoever.

"Say, aren't you brave!"

Helen was on the pavement, keeping an eye on the removal men, making sure they didn't scratch her antique sideboard with mother-of-pearl inlay. An older woman had leaned over the picket fence between their adjoining properties. She had the stout build and burst-capillary complexion of this "transitional" area's pre-gentrification residents. Before she could stop herself, Helen thought reflexively, Probably on benefits.

"I don't know how 'brave' I am when they're doing all the work," Helen said, trying to sound friendly to cover for her uncharitable assumptions.

"I mean taking that place on," the woman said. "Has quite the reputation round here, that house."

"Oh?" Helen's tone cooled. She'd hitherto nursed an aggressive lack of interest in her property's history, especially in whatever loser had lived here who was feckless enough to face foreclosure.

"Your last owner, Judith. Determined to go down with the ship, she was!"

"Except the ship," Helen nodded at her front door, "is still afloat."

The woman mistakenly imagined that the new owner was desperate to hear the story. "There's not many what realise it, but Judith weren't all that far from paying off the mortgage free and clear. But her husband had died a way back – something with the kidneys – and Ron'd brung in the bacon. Bus driver, if I recall rightly. Your bereavement payment is a one-off, your bereavement allowance last only a year, and Judith weren't old enough to draw a pension. So money got well tight. Kids were wasters. Which didn't keep her from slipping them two boys the odd tenner when she had it to spare. Only reason they ever called round, if you ask me. Judith was a generous soul. Just had her limits. She'd a long fuse on her, but she did have one fearsome temper once she was riled. All that dosh pitched to the bankers for donkey's, she weren't about to let 'em take that house off her."

"But apparently they did." With every new scrap of superfluous information, Helen's heart had steadily sunk. The last thing you wanted was a next-door neighbour who was a motor-mouth. This woman could make simply getting out the door for the smallest trip to the shops take 40 minutes. But Helen was under the misimpression that keeping her own comments to a minimum would discourage chat, when in truth terseness simply left her neighbour all the more conversational leeway to let fly.

"Not without a fight! Soon as Judith get that summons, she start hammering. A proper racket for me, you can imagine, and I come out to see she's banging up big plywood sheets over the windows, like you do for rough weather – but these boards is on the inside. They say she padlock the doors from the inside as well, top and bottom, front and back. She'd a great towering stack of food and drink in the cellar, the way them religious nutters ready for the end of the world. May not be much to look at to some – no offence intended – but to Judith it were her house, where she spend most of her marriage, where she raise her boys."

Illustration: Michael Kirkham for the Guardian

"Sounds a pity, then," said Helen, who powerfully disapproved of any such illegal sit-in. If you had to make payments, you raised the money from somewhere or accepted the consequences. Irked that her curiosity about how the story ended had been piqued despite herself, she apologised that she had to mind the removal men and fled inside.

That night, surrounded by cartons, Helen flopped into bed without having flossed. Nothing was more exhausting than moving house, and before dropping off she made the commonplace vow (as commonly broken) that she'd never pull up stakes again.

Her slumber might have been deep and dreamless, were it not for the persistent strains of Jerusalem chorusing over and over from the direction of the party wall. She'd once found the tune rousing, until a workmate at Manson & Ross had started using the first three bars as a ringtone, after which she'd found its pompous strains unbearable. She didn't want to make enemies of this woman when their properties were attached at the hip, but some laying down of ground rules was in order.

The following Sunday morning, Helen relished the Christmas sensation of unwrapping treasured keepsakes from their newsprint swaddling. Unpacking was like being given everything you owned all over again. Perching her trove of CowParade figurines and smaller "mini-moos" atop the antique sideboard felt akin to sticking a flag in the summit of Mount Everest, for the familiar bovine art reproductions made a declaration of sorts:

MY HOUSE!

read

So contented by festooning her first proper home with the dozens of touches that turned mere quadrants of space into rooms – rooms with character, rooms that had been mastered – for most of the morning she managed to ignore the insistent smell. A piercing odour of ammonia suggested that whoever had tarted up the house for sale had gone overboard with violent cleaning products, although the ammonia was contaminated with an undertone of diesel, and laced with a burnt singe. Residual wafts of detergent should have begun to dissipate; this pong was growing stronger.

If only to escape the mysterious reek, Helen took a break and headed out to her local Sainsbury's; switched on for a full day, the fridge should be cold by now. But of course she didn't make it to her front gate before the busybody next door popped out to ask how she was getting on, and to finally introduce herself as Gertrude.

"So you're a fan of Jerusalem, I gather." Helen had to force herself to bring it up.

Gertrude reared back. "Quite the opposite! Had to hear it again, I might top myself."

Helen frowned. "But I heard quite distinctly…"

"Judith, now. Couldn't tell if she specially fancied it or specially despised it, but either way that carry-on made for a fiendish weapon. Once the authorities get heavy – no surprise the bank bring in the council, and the council the police – Judith blast that song on her stereo nonstop, all hours. Never sure what she mean by it, but for me, by the end, you could shove your green and pleasant land right up England's arse."

It wasn't clear what Gertrude's game was, but at least the woman had been put on notice about her sound system.

Helen returned with an enormous shop, from which she immediately extracted the honeysuckle air freshener and sprayed the kitchen until the aerosol was half exhausted. But poorly masking the stench with artificial scent just made the room smell nauseously like a petrol station toilet. After hastily stocking the fridge-freezer, she retreated to the sitting room with chamomile tea to settle her stomach.

The photo of the Cotswolds: it was turned to the wall. The Folio Society hardbacks as well were now facing backwards, presenting a bank of blank deckle-edged pages. The cows on the sideboard had vanished. On a hunch – British burglars weren't known for eccentric reshelvings of Moby Dick – she opened the sideboard's top drawer, and there were her kaleidoscope cows, seemingly unharmed, but on their sides, shoved out of sight.

Sheer mischief! Might that Judith woman have provided Gertrude a spare key for emergencies? Yet, if so, why would her neighbour sneak inside when Helen was at the supermarket and mess with her things? Nothing seemed to have been taken, so the lady might simply have been snooping, but didn't most stealthy nosey parkers make a point of leaving everything as they found it?

Still, the ploy, whatever it was for, was oddly effective. As Helen righted the photo, reversed the Folio books and restored the resin cows to their rightful place on the sideboard, she felt more unnerved than she had been by the hostile front lock, the boiling paint job, the nail-sprouting floorboards, the bombasts of William Blake, or even that awful smell – though as she recited it, she realised that there was a list, and that it kept getting longer.

Running late for work that Monday morning, still underslept from more penetrating strains of Jerusalem, Helen whitened the coffee that would have to suffice for breakfast, only to watch the milk resurface in bobbing curds. That semi-skim wasn't a day old! But when she checked, the fridge was warm; the frozen food was melting. Surely she'd heard the comforting hum of the appliance as she unpacked dishware the day before. But now the socket was switched to the off position and everything she'd bought at Sainsbury's was ruined.

There was nothing for it but to switch the socket back to "on" and deal with the disaster after work. Perhaps she'd imagined the hum, and neither she nor the removal man who'd connected the white goods had remembered the outlet switch.

Yet when she returned from work that evening, the switch was back off. Chicken juice from the freezer pooled on the floor. Furiously, Helen pitched the breast fillets, venison burgers, sausage rolls, lamb chops, smoked salmon and packets of pre-washed baby lettuces into a bin liner. After dumping the bag of costly foodstuffs into her wheelie bin, she marched round the picket fence and pounded on Gertrude's door.

Alas, her neighbour's expression of affable innocence looked so genuine that Helen's consternation crumbled to embarrassment. If she accused this near stranger of barging into her property solely in order to turn off the refrigerator, she would sound unhinged. For that matter, confronted with the problem of a malicious intruder who must have possessed a spare key, why hadn't a capable woman like herself simply changed the lock right away?

Because when an inanimate CowParade collection freakishly transports itself from surface to drawer, safeguarding a rational explanation was tantamount to safeguarding one's sanity. So long as she didn't change the lock, she could always blame Gertrude. In the event that any further goings-on might require a logical attribution, she didn't want to change the lock.

"Sorry, I – forgot to switch on the outlet for the fridge, and now all my food's spoiled. I wondered if you might have a bit of bread and cheese, to tide me over." It was all she could come up with on the spot, though half a dozen takeaway menus had already been shoved through her letterbox.

"We can do better than that, hon. You come right in."

Gertrude's house was cluttered, laid with clashing patterned carpets and lined with hokey ceramic pigs, whose old-lady ambience might in time worrisomely confer itself on Helen's avant-garde cows. Still, the gas fire was lit, and it was a relief to feel welcome somewhere.

"Sure that outlet's being switched off was your fault?" Gertrude fished, slipping a ready-meal lasagne into the microwave.

"Who else's fault could it be? I'm on my own."

"And why would that be? Such a fine-looking girl. Don't fancy a body to keep you warm at night?"

"Oh, I've had my share of boyfriends," Helen exaggerated. "But right now I'm concentrating on my career. Enjoying my independence."

Gertrude glanced at her guest askance as she delivered a glass of lager (Helen would have preferred wine). "But what about a family? Getting late for you, I wager."

"Oh, I'm not sure children are on the cards. But they've never been a priority for me, really." The feisty assertion was undermined by a forlorn note.

As they sat down to their meal, Helen raised tentatively, "That face-off, with Judith. When she boarded the windows, and padlocked the doors from the inside. How did it end?"

"Badly, of course," Gertrude said, sorrowfully. "All manner of nasty notices pile up at the door. Officers pounding to be let in. Finally, didn't they drive up in a lorry with a battering ram, and bust through the entry. Don't know if you notice, but that front door of yours? It's spanking new. The old one was splintered to bits, like."

The old lock would have been done for as well. So much for the theory that Gertrude had a spare key. "So did they arrest her, or fine her? Say, for contempt of court?"

Gertrude sighed. "Too late for that. They found Judith collapsed in the kitchen. Probably dead a day or two. She build one of them fertiliser bombs, if you can credit it. Researched the how-to on the internet; cops found the searches on a computer she'd used down at the library. Hadn't researched it too good, mind, since heaven be praised the contraption was duff. Poor wretch were overcome by the fumes when she try to set it off. Troubled me Judith didn't take into account how blowing up her house might of taken me own with it, but she couldn't of been in what you'd call a considerate state of mind."

"It was her house," Helen filled in. "If she couldn't keep it, then no one else was going to get it either."

"Figure that's about the sum of it."

Nevertheless, sensible Helen Rutledge couldn't countenance hocus-pocus, and throughout the following several years the should continued to take precedence over a great deal of was. A washer-load of whites would come out a sickly pink, having been fouled by a pair of red socks, and Helen didn't own red socks. The dimmer switches in the breakfast room developed a constant tremble; the nervous sensation that the quavering halogen spots provided her evenings soon translated to her left eye, whose chronic twitch made clients at Manson & Ross worry that she was untrustworthy or hiding something. Electrical wiring began bulging from the plasterboard, branching in disquieting varicose veins, as if the whole house had high blood pressure.

Over time, mildew rose in a blighting speckle beside the shower stall, and to Helen the dusty pixels always formed a face – with beady, resentful eyes, frazzled hair and pressed lips – much as a vision of the Virgin Mary will appear to the devout on a piece of burnt toast. When Helen tried to wipe off the spores, she simply smeared the expression from grimace to smirk. Disrobing under the mouldy stare made her self-conscious, and alone at home with the shades drawn, Helen would bind a towel tightly under her arms to hide her breasts.

Trying to rejuvenate the dishevelled back garden, Helen planted a row of forget-me-nots, in the hope that the sheer helplessness and aching vulnerability of the tiny periwinkle blooms would protect the charming cover from harm. No such luck: the pretty little plants all withered and blackened within the week, while the garden suddenly reeked of ammonia and diesel, the smell to which she'd long before grown inured indoors.

Other misfortunes were more ruinous. During one workday, the bath spontaneously ran for hours and soaked the sitting room ceiling, which saved its collapse of soggy plaster for the moment of her return. Following some routine masonry repairs, both sinks backed up. When she swore herself blue that she would never pour wet concrete down her own kitchen drain, the plumber asked the obvious: "So who else did it?"

Even entertaining never went right. Guests spilled things, ate quickly and left early. Perhaps the sense she'd had on first entering these quarters affected others as well: they didn't feel welcome.

When she finally invited a proper date round for a summer supper – Alan was a new hire, and rather dashing, for an accountant – he seemed ill at ease from the start, having been ridiculously unsettled by the peculiar shelving of her Folio classics, which she'd given up standing spine out. "She doesn't care for Jane Austen," Helen dismissed distractedly, basting the roast. While the two chatted awkwardly in the sitting room, the meat burnt to a cinder anyway, since somehow the oven dial got nudged up to gas mark 9, and Alan had made a point of preferring his beef rare. But never mind the food, as once they sat down to a candlelit dinner on the little back porch the decking collapsed, breaking Alan's collar bone and ending their romantic evening in A&E.

Sadly, Helen's resolve not to be defeated by mere bricks and mortar came at a cost. She developed an anxious, jumpy disposition, and workmates began to avoid her at lunch. Her appearance suffered; weight loss was aging, and due to a phobia about the shower, which got scalding with no warning, as if suffering from menopausal hot flushes, her hair was often greasy and flat. Proud independence slid without her noticing to loneliness. That forlorn note that had sounded at Gertrude's about not giving "priority" to children became a dominant chord. Professionally, too, she felt increasingly perverse: despite the smorgasbord of careers from which she might have chosen when younger, she had willingly plunged up to the eyeballs into the most odious aspect of modern life.

In the office, she'd once been a notorious stickler, insistent that expenses be entered in precise amounts to the penny. Yet now her decimal points were wont to migrate willy-nilly two or three places. She would forget to include investment income, or neglect an inheritance. Consequently, one client in arrears with HMRC seemed to qualify for a substantial refund. After the client had blown his windfall on a lavish holiday in Mallorca, he returned to face an audit and then criminal prosecution. Helen was sacked.

She tried mightily to find another position, but she'd left the firm without a reference. Months went by. Formerly substantial savings depleted by stamp duty, abortive DIY and unanticipated bills from tradesmen, she soon fell behind on her mortgage payments.

Helen imagined herself a reserved person, but 21 Lansing Close had taken its toll. When the foreclosure notice from Barclays arrived, she was incandescent. Was it her fault that the job market was so anaemic? Had she not arranged monthly direct debits for year upon year? It was sheer thievery – the compulsory forfeiture of countless interest payments, a fair whack of principle, and her deposit to boot! Was it fair, for slackers to get housing from the state for free, when responsible taxpayers who fell on hard times were thrown on the street? True, she hated this house, but mutual loathing had locked them into the embrace of lovers, and it was her house to hate. Indeed, no one would ever revile this property with the ferocity of Helen Rutledge, who was not about to abdicate its deed to anyone for whom her ultimate foe, her bete noire, her personal nemesis, was merely an affordable bottom rung on the UK's most worn-out metaphor.

Dear Gertrude having passed that autumn, and the council having yet to install another tenant in the adjacent semi, Helen searched the internet with a clean conscience. Moreover, she was still capable of calling up the exactitude and attention to detail that had once distinguished her performance at Manson & Ross. Only after exhaustive cross-reference and thorough perusal of shadily inquisitive threads on ask.com and Yahoo did she settle on what appeared a foolproof recipe. So when Helen detonated her own toil and trouble, cauldron bubble, accompanied by the rousing chorus of Jerusalem, it worked.