I pull the grey blanket around my shoulders. It’s wool, and looks nice draped across the sofa, but now it scratches my neck and makes me itch. The light makes a buzzing noise you can hear upstairs – yet another thing that needs fixing – and even though I know Simon and the kids are fast asleep I’ve left it switched off, the light from my iPad making the rest of the lounge seem even darker than it really is. The wind is howling and somewhere a gate is banging. I tried to sleep, but every sound made me jump, and eventually I gave up and came downstairs.

Someone took my photo and put it in the classifieds.

That’s the only solid fact I have, and it runs through my head on a loop.

Someone took my photo.

PC Swift believes it’s my picture too. She said she’s looking into it, that she knows that sounds like a brush-off, but that she really is working on it. I wish I could trust her, but I don’t share Simon’s romanticised views of the boys and girls in blue. Life was tough when I was growing up, and round our way a police car was something to run away from, even if none of us really knew why we were running.

I tap on the screen in front of me. Tania Beckett’s Facebook page has a link to a blog; a diary written by both Tania and her mother, in the run-up to the wedding. Tania’s posts are frequent and practical: Should we have miniature gin bottles for wedding favours, or personalised Love Hearts? White roses or yellow? There are only a handful of posts from Alison, each one laid out as a letter.

My vision blurs and I blink to clear the tears. It feels wrong to read on. I can’t get Tania and her mum out of my head. I crept into Katie’s room on my way downstairs, to reassure myself she was still there; still alive. There was no rehearsal last night – she did her Saturday-evening shift at the restaurant as usual – yet Isaac brought her home regardless. They walked past the lounge window, then paused for the length of a kiss before I heard her key in the lock.

‘You really like him, don’t you?’ I asked her. I expected her to brazen it out, but she looked at me with her eyes shining.

‘I really do.’

I pause, not wanting to spoil the moment, yet unable to keep quiet. ‘He’s quite a bit older than you.’ Instantly her face hardened. The swiftness of her response made me realise she’d predicted my concern.

‘He’s thirty-one; that’s a twelve-year age gap. Simon’s fifty-four; that makes him fourteen years older than you.’

‘That’s different.’

‘Why? Because you’re an adult?’ I felt momentary relief that she understood, before I saw the flash of anger in her eyes; and the saccharine tone she’d just used was replaced with harshness. ‘So am I, Mum.’

She’s had boyfriends before, but this feels different. I can already feel her slipping away from me. One day Isaac – or some other man – will be the first person she turns to; the one she leans on when life gets too much. Did Alison Beckett feel like that?

People keep reminding me that I’m not losing a daughter, she wrote in her last diary entry.

But she did.

I take a deep breath. I won’t lose my daughter, and I won’t let her lose me. I can’t sit by and hope the police are taking this seriously; I have to do something.

Next to me on the sofa are the adverts. I’ve cut them out from the back pages of the London Gazette, carefully marking the date on each one. I have twenty-eight, spread out on the sofa cushion like an art installation.

Photographic Quilt, by Zoe Walker. It’s the sort of thing Simon would go and see at the Tate Modern.

I collected the most recent issues myself, picking up a paper every day, but the back issues I got from the London Gazette offices on Friday. You’d think you could walk in and ask for old copies, but of course it’s not that simple. They screw you for £6.99 for each issue. I should have photocopied the copies I found in Graham’s office at work, but by the time it occurred to me it was too late; they’d gone. Graham must already have put them out for recycling.

I hear a creak upstairs and freeze, but there’s nothing else and I resume my search. ‘Women murdered in London’ brings up mercifully few results, and none with photos that matched the adverts beside me. I realise quickly that headlines are little help; Google images are much more useful, and far faster. I spend an hour scrolling through photographs of police officers, crime scenes, sobbing parents, and mugshots of unsuspecting women, their lives cut short. None of them are mine.

Mine.

They’ve all become ‘mine’, these women beside me. I wonder if any of them have seen their own photo; if they – like me – are frightened, thinking someone is watching them; following them.

A blonde woman catches my eye. She’s sporting a mortarboard and gown, smiling at the camera, and I feel a glimmer of recognition. I look down at the adverts. They’re all familiar to me now, and I know exactly which one I’m trying to find.

There.

Is it the same woman? I tap my screen and the image becomes a news page – from the London Gazette’s own website, ironically.

POLICE PROBE MURDER OF WOMAN FOUND DEAD IN TURNHAM GREEN.

West London. District line, I think, trying to picture the stops. The other side of London from where Tania Beckett was killed. Could they be connected? The woman’s name is Laura Keen and there are three photos of her at the bottom of the article. Another in her graduation gown, standing between a couple who must be her parents. The second is less posed; she’s laughing and raising a glass to the camera. A student flat, I think, noting the empty wine bottles in the background, and the patterned throw used as a makeshift curtain. Finally there’s what looks like a work photo; she’s wearing a collared shirt and jacket, and her hair is neatly tied back. I make the photo larger, then pick up the advert and hold it next to the screen.

It’s her.

I don’t let myself dwell on what this means. I bookmark the page and send the link by email to myself at work so I can print out the article. I change my search term to ‘sexual assaults on women in London’, then realise it’s a fruitless quest. The images that fill my screen are of men, not women, and when I tap to access the articles the victims are nameless; faceless. I find myself frustrated by the very anonymity that is there to protect them.

My attention is caught by a headline above a CCTV image:

POLICE HUNT FOR PERVERT WHO SEXUALLY ASSAULTED WOMAN ON EARLY MORNING LONDON UNDERGROUND TRAIN.

There is scant detail.

A 26-year-old woman was travelling on the District line from Fulham Broadway when a man inappropriately touched her. British Transport Police has released a CCTV image of a man they want to trace in connection with the incident.

I look at the adverts. ‘Did this happen to one of you?’ I say aloud. The CCTV still is absurdly bad: so blurry, and so fleeting it’s impossible even to say what colour hair the man has. His own mother would be hard pushed to recognise him.

I bookmark the article, just in case, then stare at my screen. This is pointless. Like a game of Snap with half the cards missing. I turn off the iPad as I hear the unmistakable sound of footsteps on the stairs. I start to gather up the photos, but the action causes several to float on to the floor, and when Simon comes into the lounge, rubbing his eyes, I’m still picking them up.

‘I woke up and you weren’t there. What are you doing?’

‘I couldn’t sleep.’

Simon looks at the adverts in my hand.

‘From the London Gazette.’ I start to lay them out again on the cushion beside me. ‘There’s one every day.’

‘But what are you doing with them?’

‘Trying to find out what’s happened to the women in the adverts.’ I don’t tell him the real reason I’ve bought so many back issues of the Gazette, because to say it out loud would be to acknowledge that it could actually happen. That one day I’ll open a copy of the Gazette, and find Katie’s face staring out at me.

‘But you’ve been to the police – I thought they were looking into it? They’ve got intelligence systems; crime reports. If there’s a series, they’ll find the link.’

‘We know the link,’ I say, ‘it’s these adverts.’ My tone is stubborn, but deep down I know Simon is right. My Nancy Drew approach is pathetic and pointless, costing me a night’s sleep and gaining me little.

Except for Laura Keen, I remember.

I find her advert. ‘This girl,’ I say, handing it to Simon. ‘She’s been murdered.’ I open the bookmarked link and pass the iPad to him. ‘It’s her, isn’t it?’

He’s silent for a while, his face twisting into peculiar shapes as he weighs up his thoughts. ‘Do you think so? I suppose it could be. She’s got that “look”, though, hasn’t she? The one they all have at the moment.’

I know what he means. Laura’s hair is long and blonde, strategically backcombed and teased into a tousled mane. Her brows are dark and carefully defined, and her skin looks flawless. She could be any one of a thousand girls in London. She could be Tania Beckett. She could be Katie. But I’m sure she’s mine. I’m sure she’s the one in the ad. Simon passes me the iPad.

‘If you’re worried, go to the police again,’ he says. ‘But right now, come to bed. It’s three in the morning and you need rest. You’re still getting over the flu.’ Reluctantly, I put the iPad in its case and gather up the adverts again, sliding them into the case as well. I’m tired, but my mind is racing.

It’s getting light before I drop off, and when I wake around ten my head feels full and sluggish. My ears ring as though I’ve been somewhere noisy; lack of sleep making me stumble in the shower.

Our monthly Sunday roasts with Melissa and Neil have been a tradition ever since Katie, Justin and I moved in, when Melissa invited us round for Sunday lunch. Our house was crammed with boxes – some from the house I’d rented since leaving Matt; others from storage, unseen for two years – and Melissa’s clean, white house seemed enormous in comparison.

Ever since then we’ve alternated between Melissa’s and Neil’s long glossy table, and my mahogany diner, bought at Bermondsey Market for next to nothing because one of the legs was wobbly. I used to sit the kids there to do homework, and at one end you can still see the marks Justin carved with a biro in protest.

Today it’s my turn to host Sunday lunch, and I send Simon out for wine, while I make a start on the veg. Katie nicks a piece of raw carrot and I slap her hand away. ‘Will you clear the table?’

‘It’s Justin’s turn.’

‘Oh, you two, you’re as bad as each other. You can both do it.’ I yell for Justin, hearing a muffled reply I can’t understand, shouted from his bedroom. ‘Lay the table,’ I shout. He comes downstairs, still in his pyjama bottoms, his chest bare. ‘It’s gone midday, Justin, don’t tell me you’ve been asleep all morning?’

‘Give me a break, Mum, I’ve been working all week.’

I soften. Melissa’s got him working long hours at the café, but he seems to be thriving on it. That’s what a bit of responsibility does for you; although I suspect the cash backhanders might have sweetened the deal a bit.

My dining room isn’t really a room at all, but an area separated from the lounge by an archway. Lots of our neighbours have knocked through from the kitchen, or added an extension like Melissa and Neil, but we still have to carry food from the kitchen into the hall and through the lounge; a fact to which the carpet bears testimony. The big Sunday lunch every other month is the only time it’s worth it, and nowadays the only time the table gets cleared.

‘Be careful with those files,’ I tell Justin, as I walk through with a bundle of cutlery and see him dump a stack of paperwork on the sideboard. Although the dining table looks a mess I’m careful to keep everything in separate piles. There are Melissa’s two sets of accounts, each with a stack of receipts and invoices; and the books for Hallow & Reed, with Graham’s endless chits for lunches and taxi fares. ‘You’ll need the extra chair from Simon’s room,’ I remind him. He stops what he’s doing and looks at me.

‘It’s “Simon’s room” now, is it?’

Before Simon moved in we’d talked about Justin having the attic room as a sitting room. Somewhere he could have his PlayStation; maybe a sofa-bed. He was getting too old to have his friends sitting on his single bed when they came round; he needed a more grown-up space.

‘From the attic, then. You know what I mean.’

I hadn’t meant to give Simon the attic. Justin hadn’t said much when I’d told the kids I wanted Simon to live with us, and naively I’d taken his silence as acceptance. It was only after Simon moved in that the arguments started. He didn’t bring much furniture with him, but what he did have was good quality, and it seemed unfair to tell him there wasn’t space for it. We stashed it in the attic while we worked out what to do with it. It occurred to me that giving Simon a space of his own would be a good thing; it would put some distance between him and Justin, and enable me and the kids to watch telly on our own from time to time.

‘Just get the extra chair,’ I tell him.

Last night, after I’d staggered home from the shops with enough food to feed an army, Katie informed me that she wouldn’t be here for lunch.

‘But it’s roast day!’

She’d never missed one. Neither had Justin, not even when the PlayStation and his mates held more appeal than family.

‘I’m seeing Isaac.’

It’s happening, I thought. She’s leaving us. ‘So invite him here.’

‘For a family meal?’ Katie snorted. ‘No thanks, Mum.’

‘It won’t be like that. Not with Melissa and Neil here. It’ll be nice.’ She didn’t look convinced. ‘I won’t interrogate him, I promise.’

‘Fine,’ she said, picking up her mobile. ‘Although he won’t want to come.’

‘Delicious beef, Mrs Walker.’

‘Call me Zoe, please,’ I say, for the third time. You’re closer to my age than my daughter’s, I want to point out. Isaac is sitting between Katie and Melissa.

‘A thorn between two roses,’ he said, when they sat down, and I wanted to stick two fingers in my throat and make gagging noises, like a fourteen-year-old. Surely Katie isn’t taken in by this smarm? But she’s gazing at him like he’s just stepped off a catwalk.

‘How are rehearsals going?’ Melissa asks. I shoot her a grateful look. The presence of someone new has made the atmosphere stilted and artificial, and there are only so many times I can ask if everyone likes the gravy.

‘Really well. I’m amazed at how well Katie’s fitted in, and how quickly she’s got up to speed, given how late she joined us. We’ve got a dress rehearsal next Saturday, you should all come.’ He waves a fork around the table. ‘It’s really useful to have a real audience.’

‘We’d love that,’ Simon says.

‘Dad, too?’ Katie asks Isaac. I sense, rather than see, Simon stiffen beside me.

‘The more the merrier. Although you have to all promise not to heckle.’ He grins and everyone laughs politely. I’m dying for the meal to be over, and for Katie and Isaac to leave, so I can ask Melissa what she thinks of him. She’s looking at him with a glint of amusement in her eyes, but I can’t read her expression.

‘How’s the sleuthing going, Zoe?’ Neil is fascinated by the photographs in the Gazette. Every time I see him he asks if there’s any news; if the police have found anything out about the adverts.

‘Sleuthing?’

I don’t want to tell Isaac, but before I can change the subject, Katie is telling him everything. About the adverts, and my photograph, and Tania Beckett’s murder. I’m unsettled by how animated he becomes, as though she’s telling him about a film release or a new book, instead of real life. My life.

‘And she’s found another one, too. What’s the new one called, Mum?’

‘Laura Keen,’ I say quietly. I picture Laura’s graduation photo and wonder where the original is. Whether it’s on the desk of whichever journalist wrote the article, or whether it’s back on the mantelpiece in her parents’ house. Perhaps they’ve placed it glass-side down, for now, unable to handle seeing it every time they pass.

‘Where do you think they got your picture?’ Isaac asks, not picking up on my lack of enthusiasm to discuss it. I’m surprised at Katie for encouraging him, and put it down to a desire to impress. Neil and Simon are eating in silence; Melissa shooting me sidelong glances every now and then, to check I’m okay.

‘Who knows?’ I’m trying to make light of it, but my fingers feel clumsy and my knife clatters against my plate. Simon pushes his empty plate away and leans back, reaching one arm out to rest on my chair. To anyone else he is just relaxing, replete after a big meal, but I can feel his thumb circling reassuringly on my shoulder.

‘Facebook,’ Neil says, with a confidence that surprises me. ‘It’s always Facebook. Most of the ID frauds nowadays use names and photos lifted from social media.’

‘The scourge of modern society,’ Simon says. ‘What was that firm you worked for a few months ago? The stockbrokers?’ Neil looks blank, then gives a short bark of laughter. ‘Heatherton Alliance.’ He looks at Isaac, the only one who hasn’t heard this story. ‘They brought me in to gather evidence relating to insider trading, but while I was there they had one of those initiation ceremonies for a new female banker. Real Wolf of Wall Street stuff. They had a Facebook group going – a private forum so they could decide what to do to her next.’

‘How awful,’ Isaac says, although his eyes don’t match his tone. They’re bright, interested. He catches me looking at him, and reads my mind. ‘You think I’m being ghoulish. I’m sorry. It’s the curse of the director, I’m afraid. Always imagining how a scene might play out, and that one – well, that would be truly extraordinary.’

The conversation has sapped my appetite. I put down my knife and fork. ‘I hardly use Facebook. I only joined to stay in touch with family.’ My sister Sarah lives in New Zealand, with a tanned, athletic husband and two perfect children I’ve only met once. One’s a lawyer and the other works with disabled children. It doesn’t surprise me that Sarah’s kids have turned out so well; she was always the golden girl when we were growing up. My parents never said it, but it was always in their eyes: why can’t you be more like your sister?

Sarah was studious; helpful round the house. She didn’t play her music loud or sleep till noon at the weekends. Sarah stayed on at school, left with good grades and a place at secretarial college. She didn’t drop out, pregnant. Sometimes I wonder what would have happened if she had done; if our parents would have been as hard on her as they were on me.

Pack your bags, my dad said, when he found out. Mum started crying, but whether it was because of the baby or because I was leaving, I couldn’t tell.

‘You’d be surprised what you can get from Facebook,’ Isaac says. He pulls his phone – a sleek iPhone 6s – from his pocket and swipes deftly across the screen. Everyone watches him, as though he’s about to perform a magic trick. He flashes the screen towards me and I see the blue-and-white branding of Facebook. My name is written in the search field, and beneath it is row upon row of Zoe Walkers, each with a thumbnail photo. ‘Which one is you?’ he says, scrolling through them. He taps through to the second page.

‘There.’ I put my hand out to point. ‘That one, third from the bottom. The one with the cat.’ It’s a picture of Biscuit sunning himself on the gravel at the front of the house. ‘You see,’ I say triumphantly, ‘I don’t even use my own photo for my profile. I’m quite a private person, really.’ Not like my kids, I think, who let their whole lives play out on Instagram, or Snapchat, or whatever’s flavour of the month right now. Katie’s forever taking selfies, pouting this way and that, then swiping through endless filters to find the most flattering.

Isaac opens my page. I don’t know what I expected to see, but it wasn’t my entire Facebook profile.

‘Strictly,’ I explain, embarrassed to see my life reduced to one-liners about TV shows and hellish commutes. I’m alarmed by the ease with which he appears to have accessed my account. ‘How have you been able to log on as me?’

Isaac laughs. ‘I haven’t. This is what anyone can see if they click on your profile.’ He catches sight of my horrified face. ‘Your privacy settings are wide open.’ To prove it, he clicks on the ‘about me’ tab, where my email address is there for anyone to see. Studied at Peckham Comprehensive, it says, as though that were something to be proud of. Worked at Tesco. I half expect it to say ‘knocked up at seventeen’.

‘Oh God! I had no idea.’ I vaguely remember filling out these details: the jobs I’ve had, the films I like and the books I’ve read, but I’d thought it was just for me; a sort of online diary.

‘The point I’m trying to make,’ Isaac says, clicking once more, on a tab marked ‘photos of Zoe’, ‘is if someone wanted to use a picture of you, there are plenty to choose from.’ He scrolls through dozens of images, most of which I’ve never seen before.

‘But I haven’t uploaded these!’ I say. I see a photo of me from behind, taken at a barbecue at Melissa’s and Neil’s last summer, and consider whether my bum is really that big, or if it’s simply an unflattering angle.

‘Your friends have. All these photos’ – there must be dozens of them – ‘are ones other people have uploaded and tagged you in. You can untag yourself if you want, but what you really need to do is sort out your privacy settings. I can help you, if you want?’

‘It’s fine. I’ll sort it out.’ Embarrassment is making me abrupt, and I make myself say thank you. ‘Has everyone finished? Katie, love, will you give me a hand clearing the table?’ Everyone starts stacking plates and carrying dishes out to the kitchen, and Simon squeezes my hand before very obviously changing the subject.

When everyone has gone I sit in the kitchen with a cup of tea. Simon and Katie are watching some black-and-white movie, and Justin has gone out to see a mate. The house is quiet and I bring up Facebook on my phone, feeling as though I’m doing something wrong. I look at the photos, recognising the album Isaac showed me on his own phone. I scroll through them slowly. Some of the photos aren’t even of me, and eventually I understand I’ve been tagged in pictures of Katie, or old school photos from back in the day. Melissa’s tagged me and a bunch of other people in a photo of her own legs, taken by the pool on a holiday last year.

Jealous, girls???!! reads the caption.

It takes me a while, but finally I find it. The photo from the advert. I let out a breath. I knew I wasn’t going mad – I knew it was me. Facebook tells me the photo was posted by Matt, and when I check the date I see it was three years ago. I follow the link and find twenty or thirty photos, uploaded en masse after my cousin’s wedding. That’s why I wasn’t wearing my glasses.

This photo is really of Katie. She’s sitting next to me at the table, smiling at the camera with her head tilted to one side. I’m watching her, rather than the camera. The picture in the advert has been carefully cropped, taking out most of the dress I’d have instantly recognised as one of my few party outfits.

I imagine someone – a stranger – scrolling through my photos, looking at me in my posh frock, at my daughter, my family. I shiver. The privacy settings Isaac mentioned aren’t easy to locate, but eventually I find them. I systematically lock down every area of my account; photos, posts, tags. Just as I finish, a red notification blinks at the top of my screen. I tap on it.

I stare at it for a second, then press delete.