‘You tripped me up!’ Isaac says, looking up at Megan. He puts a hand on the road to push himself up. The small crowd of people that had gathered to watch the excitement begins to separate.

‘Yes,’ she says. She stoops and begins picking up the scattered coins littering the road. I help her, if only to stop myself from staring at Isaac, who appears both mildly affronted and amused by what’s happened. ‘You were chasing her,’ Megan adds, with a shrug that suggests it was really the only course of action available to her.

‘I was catching up with her,’ Isaac says. ‘There’s a difference.’ He stands up.

‘Megan, this is my daughter’s …’ I trail off, not knowing what to call him. ‘We know each other,’ I finish.

‘Right.’

Megan doesn’t seem embarrassed. Perhaps, in her world, the fact that Isaac and I know each other means nothing. He could still have been chasing me.

He could still have been chasing me.

I brush the thought off as ridiculous before it can take hold. Of course he wasn’t chasing me.

I turn to him. ‘Why are you here?’

‘Last time I checked,’ he says, ‘it was a free country.’ He’s smiling as he says it, but nevertheless irritation seeps through me. I assume it registers on my face, because he decides to be serious. ‘I’m on my way to see Katie.’

‘Why were you running?’ I’m emboldened by the presence of Megan, who has stepped away but is watching my interrogation with interest, her guitar held loosely at her side.

‘Because you were running,’ he says. It’s so logical that I’m no longer sure how I feel. I hear the sound of police sirens in the distance. ‘I knew you were on edge about the adverts in the Gazette, and then Katie told me about the website. When I saw you running I thought someone had frightened you.’

‘Yes, you!’ My heart is still racing, and I feel the heady buzz of an adrenaline spike. The sirens grow louder. Isaac holds his hands skywards in an I can’t win gesture, annoying me further. Who is this man? The sirens are deafening; I look up Anerley Road and see a police car coming towards us, its lights flashing. The car pulls up ten metres in front of us; the siren is extinguished, mid-wail.

Will Isaac run? I wonder, and I realise I’m hoping he does. I want this to be it; the end of the adverts, the website, the fear. But he puts his hands in his pockets and looks at me, shaking his head as though I’ve done something utterly incomprehensible. He walks towards the officers.

‘This lady’s had a bit of a scare,’ he explains, and I’m so filled with rage I can’t speak. How dare he act as though he’s in charge? Dismiss what just happened as a bit of a scare?

‘Your name, sir?’ The policeman gets out a notebook, while his colleague – a woman – walks towards me.

‘He was chasing me,’ I tell her, and just saying it makes me think that it’s true. I start telling her about the adverts, but she already knows. ‘He began following me at Cannon Street, and when we got to Crystal Palace he started running after me.’ Had he run first, or had I? Does it matter? The policewoman takes notes, but seems uninterested in the detail.

A car pulls up behind the police car, and I recognise DI Rampello behind the wheel. PC Swift is with him, and I feel a surge of relief, knowing I won’t have to convince her about what just happened. DI Rampello speaks to the policewoman, who puts away her notebook and joins her colleague.

‘Are you okay?’ Kelly asks.

‘I’m fine. Except for Isaac scaring me witless.’

‘You know him?’

‘His name’s Isaac Gunn – he’s my daughter’s boyfriend. She’s in a play at the moment and he’s the director. He must have downloaded my commute from the website.’ I catch an exchange of glances between them, and know exactly what they’re going to say.

‘The website provides users with a means of following strangers,’ PC Swift says. ‘Why would someone you know need to use it?’

DI Rampello looks at his watch. ‘It’s not even midday. Your commute says you leave work at five thirty.’

‘My boss sent me home. That’s not a crime, is it?’

He is more patient than my tone deserves. ‘Of course not. But if Isaac Gunn had downloaded your commute and was using it to follow you, he wouldn’t have been successful today, would he? You’ve not stuck to the script.’

I’m silent. I think about the footsteps I heard at Cannon Street; the glimpse of an overcoat on the District line. Was it Isaac I saw then? Or someone else? Could I have imagined the feeling of being followed?

‘You should at least question him. Find out why he was following me; why he didn’t try to get my attention when he first saw me.’

‘Look,’ DI Rampello says gently. ‘We’ll bring Gunn in for a voluntary interview. Find out if there’s any connection with the website.’

‘And you’ll let me know?’

‘As soon as we can.’

Across the road I see Isaac getting into the police car.

‘Can we give you a lift home?’ PC Swift says.

‘I’ll walk, thank you.’

Megan reappears at my side as DI Rampello and PC Swift drive away, and it’s only then I realise she had melted away the second the police arrived. ‘So you’re all right, then?’

‘I’m fine. Thanks for looking out for me today.’

‘Thanks for looking out for me every day,’ she counters, smiling.

I throw a coin into her guitar case as she starts strumming the chords for a Bob Marley song.

The evening is crisp and cold. They’ve been forecasting snow for days and tonight I think it’s on its way. Thick white clouds hang above me, and the road sparkles with early frost. I replay the journey home from work in my head, trying to pinpoint the exact moment I knew someone was following me; the exact moment I broke into a run. The act of remembering is a distraction from what is really troubling me: what the hell am I going to say to Katie? That her boyfriend was stalking me? The closer I get to home, the more I doubt myself.

When I open the door I hear the radio playing in the kitchen, Simon’s tuneless accompaniment fading in and out in proportion to his familiarity with the lyrics. I haven’t heard him singing for a long time.

The front door bangs behind me; the singing stops.

‘I’m in here!’ Simon calls, unnecessarily. When I join him I see he’s set the kitchen table for lunch. ‘I thought you might like something hot,’ he says. There’s a pan bubbling on the hob; prawn risotto with asparagus and lemon. It smells delicious.

‘How did you know I’d be home early?’

‘I phoned you at work and your boss told me he’d sent you home.’

I think how much I’d like to live without someone monitoring my every move, then instantly feel ungrateful. The police, Graham, Simon: they’re trying to keep me safe, that’s all.

‘I thought he was going to sack me.’

‘Let him try. We’ll have him in an unfair dismissal tribunal before you can say “to let”.’ He grins at his own joke.

‘You’re very chipper. Can I assume the job interview went well?’

‘I had a call even before I’d reached the Tube station. They’ve invited me in tomorrow for a second interview.’

‘That’s fantastic! Did you like them? Does the job sound good?’ I sit down and Simon places two steaming bowls of risotto on the table. I have the sudden hunger that follows a period of high adrenaline, but the first mouthful turns to acid in my stomach. I have to tell Katie. She’ll be waiting, wondering where Isaac is. Worrying, maybe.

‘Everyone’s about twelve years old,’ Simon is saying, ‘the circulation’s only eight thousand, and I could do the job blindfolded.’ I open my mouth to ask about Katie, but he misreads my intention and cuts me off. ‘But, like you said yesterday, it’s a job, and the hours would be better than at the Telegraph. No weekend working, no late shifts covering the news desk. It would give me a chance to work on my book.’

‘It’s great news. I knew something would come up.’ We eat in silence for a while. ‘Where’s Katie?’ I say, as though it’s only just occurred to me.

‘In her room, I think.’ He looks at me. ‘Is something wrong?’

And at that moment I decide I’m not going to tell him.

Let him focus on tomorrow’s interview without worrying that he should be staying home to look after me; without worrying that Katie is involved with a potential stalker. I ignore the insistent voice in my head; the voice that says I don’t want to tell him because I’m not even certain I’m right.

I hear footsteps on the stairs and the unmistakable sound of Katie’s shoes heading towards the kitchen. She walks in, staring at her phone. ‘Hey, Mum. You’re home early.’

I look between her and Simon; a rabbit in the path of an oncoming car, wondering which side of the road to run to. Katie flicks on the kettle; frowns at her phone.

‘Everything okay, love?’

Simon looks at me curiously, but doesn’t say anything. If he can hear the note of anxiety in my voice I know he’ll put it down to what’s been going on. The ‘stress’ with which Graham has signed me off work.

‘Isaac was supposed to be coming over, but he texted to say something’s come up,’ Katie says. She seems surprised, rather than upset, and I know it’s because she isn’t used to being let down. I hate myself for being the one to do it to her.

I had assumed the police would have taken Isaac’s phone straight away. I imagine the conversation in the police car, or in custody.

I need to get a message to my girlfriend.

One text. Then hand over the phone.

Maybe it was nothing like that. Maybe they all got along famously: Isaac charming the female officer; getting chummy with her male colleague.

I really need to let my girlfriend know what’s happened – she’ll be worried. You’ve seen her mother, she’s not stable …

‘Did he say what had come up?’ I ask Katie.

‘Nope. It’ll be something to do with the show. He’s always working – I suppose you have to be, when you’re self-employed. I hope everything’s all right though – it’s curtain up in seven hours!’ She takes a Pot Noodle upstairs and I rest my fork on the edge of my bowl. It’s the opening night tonight. How could I have forgotten? What if Isaac is still with the police?

‘Not hungry?’ Simon says.

‘Sorry.’

I’ve dug myself into a mess I don’t know how to get out of, and for the rest of the day I prowl the house, offering Katie cups of tea she doesn’t want, braced for the moment she tells me she knows I had Isaac hauled off in a cop car.

A voluntary interview, I remind myself. He wasn’t arrested. But I know the distinction will mean little to Isaac. Or to Katie. At five Matt picks up her to take her to the theatre.

‘She’s just getting her stuff,’ I say. Matt stands on the step, and I feel the cold slide in through the open door. ‘I’d ask you in, but it’s … you know, it’s awkward.’

‘I’ll wait in the cab.’

Katie runs down the stairs, pulling on her coat. She kisses me.

‘Break a leg, love. Isn’t that what they say?’

‘Thanks, Mum.’

As Matt drives off, my mobile rings; PC Swift’s number flashing on the screen. I take my phone upstairs, pushing past Justin on the stairs with a hurried, Excuse me. I go up to Simon’s office and close the door behind me.

Kelly Swift doesn’t bother with niceties. ‘We’ve let him go.’

‘What did he say?’

‘What he said to you. That he saw you on the Tube and thought you looked anxious. He said you kept looking around you; that you seemed jumpy.’

‘Did he admit to following me?’

‘He said he was going to see your daughter, so naturally he walked the same way. When you broke into a run he was concerned, so he ran to catch you up.’

‘Why didn’t he come and speak to me?’ I demand. ‘When he saw me on the Tube? He could have approached me then.’

PC Swift hesitates. ‘He seems to think you don’t like him.’ There’s a post-it note peeling away from Simon’s computer screen, and I press the corners down with my thumb. ‘We’ve got his phone and his laptop, Zoe – he was quite happy to let us have access – and at first glance there’s nothing linking him to find the one dot com. Cyber Crime will investigate more thoroughly over the next few hours, and of course I’ll let you know if they turn anything up.’ She pauses again, and when she speaks her voice is softer. ‘Zoe, I don’t think he’s got anything to do with the website.’

‘Oh God, what have I done?’ I shut my eyes, as if that will help me block out the mess I’m making of everything. ‘My daughter’s never going to forgive me for this.’

‘Isaac was very understanding about the mix-up,’ PC Swift says. ‘He knows you’ve been under a lot of stress. I got the impression he was happy to keep things between you and him.’

‘He’s not going to tell Katie? Why would he do that?’

She exhales, and I think I detect a note of exasperation in her voice. ‘Maybe he’s just one of the good guys, Zoe.’

The following day the house is quiet when I get up. It’s strangely bright in our bedroom and when I open the curtains I see that the promised snow has come. The roads are already clear – grit and traffic making short work of the overnight fall – but the pavements and gardens, the roofs and stationary cars, are covered in two inches of soft white snow. Fresh flakes drift past the window to cover the footprints on the path outside.

I kiss Simon on the lips. ‘It’s snowing!’ I whisper, like a child wanting to go out and play. He smiles without opening his eyes and pulls me back into bed.

When I get up again the snow has stopped. Justin has another long shift at the café, and Katie is sleeping off her opening night. She’s left a note for me propped against the kettle.

He didn’t tell her. I let out a slow breath.

I’ll need to speak to him. Apologise. But not today.

‘What time’s your interview?’ I ask Simon.

‘Not till two o’clock, but I thought I’d go in this morning and pick up a few back issues so I can mug up a bit over lunch. You don’t mind, do you? You’ll be all right here?’

‘I’ll be fine. Katie’s home. I’m going to have a tidy-up, I think.’ The house is a mess; the dining table we sat around only two weeks ago has reverted to its usual cluttered state. Last night I tipped out the receipts and invoices Graham gave me, but I can’t make a start on his books until I’ve cleared up.

He kisses me goodbye and I wish him luck. I hear him whistling as he unlocks the front door, and I smile to myself.

Katie emerges around eleven. Despite the bags under her eyes, and the line of kohl she hasn’t completely removed, she looks radiant.

‘It was amazing, Mum.’ She takes the tea I hand her and follows me into the dining room, where she pulls out a chair and sits down, hugging her knees to her chest. Her feet are encased in huge fluffy boots. ‘I didn’t need a single prompt, and at the end, someone actually stood up! I think it was someone Isaac knew, but even so.’

‘So there’s some money coming in, then?’

‘There will be. We have to pay the theatre hire, and box office costs, and that sort of thing first.’ I say nothing. I wonder if Isaac’s already taken his cut. Katie suddenly looks at me.

‘Why aren’t you at work?’

‘I’m off sick.’

‘Mum, why didn’t you say? You shouldn’t be doing that. Here, let me.’ She leaps up and takes a pile of files from me, looking around and eventually dumping them back on the table where they were. A receipt wafts off the table and on to the floor.

‘I’m not that sort of sick. Graham’s signed me off for a bit. Just while the police sort out this website nonsense.’ It feels good, dismissing it as nonsense. Empowering, Melissa would call it. I bend down to pick up the receipt, which has floated under the table.

Diet Coke £2.95.

I don’t know if it’s come from one of the piles of accounts, or whether it’s just another of the receipts we all crumple up and dump on the table.

The receipt is for a place called Espress Oh! A terrible name for a café, I think. It’s trying too hard; the laboured pun making you cringe, like those Curl Up and Dye hairdressers, or that salad bar in E16 called Lettuce Eat. I turn the receipt over and see the numbers ‘0364’ written in a hand I don’t recognise. A PIN, perhaps?

I put the receipt to one side. ‘Leave all this, love,’ I tell Katie, who is still moving papers around with helpful enthusiasm but little efficiency. ‘It’s easier if I do it. That way nothing gets mixed up.’ I let her tell me about the opening night – about the four-star review from Time Out, and the rush she got when they came on stage for a second curtain call – while I tidy and sort and rearrange the papers on the dining table. The process makes me feel calmer, as though simply by tidying the house I can get some control over my life.

I’d never have asked Graham for time off, and I’m grateful to him for forcing my hand. At least now I can stay at home while the police do whatever they’re doing to solve this case. I’m through with detective work. Let them take the risks; I’m staying here, where it’s safe.