The adverts are consuming me; filling my head and making me paranoid. Last night I dreamed it was Katie’s face in the classifieds. Katie’s face in The Times a few days later; assaulted, raped, left for dead. I woke up drenched in sweat, unable to bear even Simon’s arms around me until I’d crossed the landing and seen her with my own eyes, sleeping soundly.

I throw my usual ten-pence coin into Megan’s guitar case.

‘Have a great Monday!’ she calls. I make myself smile back. The wind whips round the corner, and I’m amazed she’s able to play with fingers that are blue with cold. I wonder what Simon would say if I brought her home for tea one day; whether Melissa might put aside a portion of soup for her from time to time. I hold a conversation in my head as I go through the ticket barriers, practising the offer of a hot meal without making it sound like charity, worrying I might offend Megan.

I’m so caught up in my thoughts I don’t instantly notice the man in the overcoat: I can’t even be sure he was watching me before I saw him. But he’s watching me now. I walk down the platform as the train arrives, but when I step on to the train and sit down I see him again. He’s tall and broad, with thick grey hair and a beard to match. It’s neatly trimmed, but there’s a speckle of blood on his neck where he’s cut himself shaving.

He’s still looking at me, and I pretend to study the Tube map above his head, feeling his eyes travel down my body. It makes me uncomfortable, and I look down at my lap, feeling self-conscious and not knowing what to do with my hands. I guess him to be in his fifties; in a well-cut suit and an overcoat to beat the weather, which is threatening the first flurry of snow. His smile is too familiar – proprietary.

The schools must be out today: the trains are far less crowded than usual. At Canada Water enough people get off to leave three seats free opposite me. The man in the suit takes one of them. People do look at you on the Tube – I do it myself – but when you catch their eye, they look away, embarrassed. This man isn’t looking away. When I look at his face – and I won’t do so again – he holds my gaze challengingly, as though I should be flattered by the attention. I wonder, fleetingly, if I am, but the fluttering sensation in my stomach is anxiety, not excitement.

Transport for London have been running a video campaign. It’s called ‘report it to stop it’ and it’s about sexual harassment on the Underground. You can report anything that makes you uncomfortable, it says. I imagine calling a police officer, right now. What would I say? He keeps looking at me …

Looking at someone isn’t a crime. At the back of my mind is the group of kids at Whitechapel – the lad in the trainers I was so convinced was running after me. Imagine if I’d have called the police then; if I’d have shouted for help. Despite the logic of this argument I can’t shake the unsettled feeling.

It’s not just him – this arrogant man taking possession of me with his eyes. It takes more than a man to make me anxious. It’s everything. It’s the thought of Cathy Tanning, asleep on the Tube while someone ransacks her bag. It’s Tania Beckett, lying strangled in a park. It’s Isaac Gunn, and the confident way he’s pushed his way into Katie’s life; into my house. I looked at his Facebook profile last night, after everyone left, and was disappointed to find it locked down so securely that all I could see was his profile picture. I stared at it; at the confident smile, showing even white teeth, and the wavy black hair flopping nonchalantly over one eye. Film-star looks, undoubtedly, but making me shiver, not swoon; as though he’d already been cast in the role of the villain.

The man in the suit stands up to let a pregnant woman sit down. He’s tall, and his hand slips easily through the strap hanging from the ceiling, the loop encircling his wrist as he grips it higher up, where it meets the ceiling of the carriage. He’s not looking at me any more, but he’s barely six inches away from me and I pick up my bag from between my feet and hug it to me, thinking again of Cathy Tanning and her pickpocket. The man glances at his watch, then away, gazing without interest at something further down the carriage. Someone else moves, and the man shifts slightly. His leg touches mine, firmly, and I jump as though I’ve been scalded. I move away, twisting awkwardly in my seat.

‘Sorry,’ he says, looking straight at me.

‘No problem,’ I hear myself say. But my heart is racing; blood humming in my ear as though I’ve been sprinting.

I stand up at Whitechapel. It’s obvious I’m getting off, but the man doesn’t move and I have to squeeze past him. For a second I’m pressed against him and I feel a touch on my thigh so light I can’t be certain it was there at all. There are people all around me, I tell myself. Nothing can happen. But I almost trip in my haste to leave the train. I look behind me as the doors close, more confident with some distance between me and the man who was watching me.

He isn’t on the train.

Perhaps he’s sitting down, I think, gifted a seat by a passenger disembarking. But there’s no one in the carriage with a beard. No one in a dark grey overcoat.

The platform is clearing; commuters rushing to get their next train, tourists looking for the exit, bumping into each other as they pay more attention to maps than their surroundings. I stand, rooted to the spot, as they jostle their way past.

And then I see him.

Standing as still as I am, on the platform about ten yards further down, between me and the exit. Not watching me; looking at his phone. I fight to keep my breathing under control. I need to make a decision. If I walk past him and carry on with my journey he might follow me. But if I hang back and let him go ahead, he might stay. The platform is practically empty; in a moment it will be just the two of us. I have to decide now.

I walk. Eyes forward. Walking quickly, not running. Don’t run. Don’t let him see you’re scared of him. He’s standing in the centre of the platform, a bench behind him that means I have to pass in front. As I grow near I sense his eyes on me.

Three feet away.

Two.

One.

I can’t help myself; I break into a run. I head for the exit, my handbag banging against my side, not caring what I look like. I half expect him to follow me, but when I reach the section of tunnel that will take me to the District line, I turn and see him still standing on the platform, watching me.

I try to concentrate on work, but my head won’t comply. I find myself staring blankly at my screen, trying to remember the admin login for our accounts package. A man comes in to ask for details for office premises for lease and I end up giving him a sheaf of details for properties for sale instead. When he comes back to complain I burst into tears. He is politely sympathetic.

‘It’s not the end of the world,’ he says, when he finally has what he wants. He looks vaguely around for some tissues, relieved when I tell him I’m absolutely fine and would really rather be on my own.

I jump as the door opens and the bell above the frame jangles. Graham looks at me strangely.

‘Are you all right?’

‘Fine. Where have you been? There’s nothing in the diary.’

‘There’s nothing in the office diary,’ he corrects, taking off his coat and hanging it on the stand in the corner. ‘There’s always something in my diary.’ He smoothes his suit jacket over his belly. Today’s waistcoat and jacket are green tweed, teamed with red trousers; the ensemble makes him look like a Country Living model gone to seed. ‘A coffee would be nice, Zoe. Have you seen the paper?’

I grit my teeth and head for the kitchen. On my return I find him in his office with his feet on the desk, reading the Telegraph. I don’t know if it’s the adrenaline from this morning, or my annoyance at being the only one at Hallow & Reed who seems to do any work, but I start speaking before I have a chance to filter my words.

‘The London Gazette. You had a huge pile of them – twenty at least – in your office. What were they for?’

Graham ignores me, his raised eyebrows the only indication he’s heard me.

‘Where are they now?’ I demand.

He swings his feet off the desk and sits upright, with a sigh that suggests my outburst is tedious, rather than offensive. ‘Pulped, I would imagine. Isn’t that where the rest of the newspapers go? Destined for the loo-roll shelves at some budget supermarket.’

‘What were you doing with them, though?’ It’s been nagging at me; that small voice in my head reminding me of what I saw, of those newspapers stacked up on his desk. I remember the moment I saw Cathy Tanning’s photo; the moment of recognition as I put a name to the face.

Graham sighs. ‘We’re a property firm, Zoe. We sell and rent properties. Offices, shopping malls, industrial units. How do you think people hear about our properties?’

I assume it’s a rhetorical question, but he waits expectantly. Not content with patronising me, he’s going to make a fool of me, too.

‘In the newspaper,’ I say, and the words come out staccato, silent full-stops between each one.

‘In which newspaper?’

I clench my fists by my side. ‘In the Gazette.’

‘And where do you think our competitors advertise?’

‘Okay, you’ve made your point.’

‘Have I, Zoe? I’m a little concerned that you don’t seem to know how this business works. Because if you’re finding it hard to understand, I’m sure I could find another office manager with bookkeeping skills.’

Checkmate.

‘I do understand it, Graham.’

His lips stretch into a smile. I can’t afford to lose my job, and he knows it.

I buy a magazine on my way home from work, determined not to even pick up a copy of the Gazette. The station is rammed; winter coats making everyone seem twice the size. I push my way along the platform to my usual spot, the extra effort worth it for the time I will gain when I change for the Overground. Beneath my feet I feel the bumpy surface installed to help blind people; my shoes protrude just beyond the yellow line and I shuffle back as far as the swell of commuters will allow. I look at the cover of my magazine, filled with increasingly impossible headlines.

MEET THE GRANDMOTHER WHO CHEATED DEATH – THREE TIMES!

I MARRIED MY SON’S WIFE!

MY TEN-MONTH-OLD BABY TRIED TO KILL ME!

I feel the rush of warm air on my face that tells me the train is seconds away. A deep rumble builds from within the tunnel and my hair blows across my face. I put up a hand to brush it aside, apologising as my arm makes contact with the woman next to me. Another raft of commuters push their way on to the platform; the bodies around me move more tightly together. I take a single step forward, less by choice than by necessity.

The front of the train fills the tunnel and I roll up my magazine into my hand. I’m trying to slot it into my handbag when I lose my balance; falling fast towards the edge of the platform. I register a solid shape between my shoulder blades; an elbow, a briefcase, a hand. I feel the bumps beneath my feet as I trip forward; the movement of dirt from beneath the tracks caused by the draught from the oncoming train. I feel a sensation of weightlessness, as my centre of gravity tips forward, my feet no longer anchored firmly on the ground. I see, coming into sharp focus, the train driver, and I register the horror on his face. We’re surely both thinking the same thing.

There’s no way he can stop in time.

Someone screams. A man shouts. I squeeze my eyes tightly shut. There’s a screech of metal on metal and a roaring in my ears. I feel a sharp pain as my shoulder is wrenched back and my body twists round.

‘Are you okay?’

I open my eyes. There’s a cluster of concern around me, but the train doors are open and commuters are in a hurry. They melt away, and the train completes its exchange of passengers and begins to move.

Again, more urgent this time. ‘Are you okay?’

The man in front of me has thick grey hair and a neatly trimmed beard. He is tall enough for me to see the speck of congealed blood to the left of his Adam’s apple. I take an involuntary step backwards and he grabs hold of my arm.

‘Steady – I’m not sure I can handle two rescues in one day.’

‘Rescue?’ I’m trying to process what just happened.

‘You’re right, rescue’s probably an exaggeration.’ He gives a self-deprecating grin.

‘It’s you,’ I say stupidly. He looks at me blankly. ‘From the District line this morning.’

‘Oh,’ he smiles politely, ‘right. I’m sorry, I don’t …’

I’m caught off guard. I’d been so sure he was following me this morning. But he wasn’t watching me. He doesn’t even remember me.

‘No, well, why would you?’ Now I feel stupid. ‘I’ve made you miss the train. I’m sorry.’

‘There’ll be another along in a minute.’ Since we’ve been talking the platform has filled up again with people jostling to be at the front of the queue, clusters forming at regular intervals down the line, behind commuters with inside knowledge of where the doors will open.

As long as you’re all right.’ He hesitates. ‘If you need support there are people who listen … the Samaritans, maybe.’

I’m confused, then I realise what he’s saying. ‘I wasn’t trying to kill myself.’

He isn’t convinced. ‘Okay. Well, they’re there to help. You know, if you need them.’

Another burst of warm air; the rumble of an approaching train.

‘I’d better …’ He gestures vaguely towards the tracks.

‘Of course. I’m sorry to have kept you. And thank you again. I’m going to walk, I think. Get some fresh air.’

‘It was a pleasure to meet you …’ he closes with a question.

‘Zoe. Zoe Walker.’

‘Luke Friedland.’ He offers a hand. I hesitate, then shake it. He steps on to the train; smiles politely as the doors close and the train pulls away. I see a flash of a smile before the carriage disappears into the tunnel.

I don’t walk. I wait for the next train, taking care to stand well away from the edge of the platform. The thought that has been lurking at the corner of my mind finally takes shape.

Did I trip?

Or was I pushed?