‘You weren’t always such a dick,’ Fatima replies, but there’s no rancour in her voice, and she is smiling too. She reaches across the table and punches Thea lightly on the arm, and Thea laughs, and her real, true smile – the one which is wide and generous and full of self-mockery – flashes out in spite of herself.

‘Liar,’ she says, still grinning, and the tension leaches out of the air, like static electricity discharging into the ground with a harmless crackle.

I don’t know what time it is when I get up from the table to go to the bathroom. It must be long past midnight. I look in at Freya on my way back, and she is sleeping peacefully, her arms and legs sprawled in complete relaxation.

As I make my way down the curving stairs to where my old friends sit, I am overwhelmed by a sharp pang of déjà vu. Fatima, Thea, Kate, they are seated in their old accustomed places, and for a moment, their heads bent around the flickering light of the candle, they could be fifteen again. I have the strangest impression of a gramophone record that has skipped, retracing over the echoes of our former selves, and I feel the ghosts of the past crowd in, Ambrose … Luc … My heart clutches in my chest, an almost physical pain, and for a moment – a brief, stabbing moment – a picture flashes before my eyes, a scene I have tried so hard to forget.

I shut my eyes, put my hands to my face, trying to scrub the image away – and when I open them again it’s just Thea, Fatima and Kate there. But the memory remains – a body, stretched out on the rug, four shocked white faces, stained with tears …

There is a chilly touch on my hand, and I swing round, my heart thumping as I survey the stairs, winding up into darkness.

I’m not sure who I was expecting – there is no one here but us, after all – but whoever it was, they are not there – just the shadows of the room, and the faces of our former selves looking out from the walls.

Then I hear Kate’s low laugh, and I realise. It’s not a ghost, but a shadow – Kate’s dog, Shadow, his cold nose against my hand, looking plaintive and confused.

‘He thinks it’s bedtime,’ Kate says. ‘He’s hoping someone will take him out for a last walk.’

‘A walk?’ Thea says. She takes out another Sobranie, and puts the gold tip between her lips. ‘Screw that. I say a swim.’

‘I didn’t bring my costume,’ I say automatically, before I work out what her raised eyebrow and wickedly provocative expression means, and I start to laugh, half reluctantly. ‘No way, and anyway, Freya’s asleep upstairs. I can’t leave her.’

‘So don’t swim far!’ Thea says. ‘Kate. Towels!’

Kate stands up, takes a gulp from the glass of wine on the table in front of us, and goes to a cupboard near the stove. Inside there are threadbare towels, faded to shades of pastel grey. She throws one at Thea, one at me. Fatima holds up her hands.

‘Thanks, but –’

‘Come on …’ Thea drawls. ‘We’re all women, right?’

‘That’s what they all say, until some drunk comes along on the way back from the pub. I’ll sit it out, cheers.’

‘Suit yourself,’ Thea says. ‘Come on, Isa, Kate, don’t let me down, you losers.’

She stands too, and begins to unbutton her shirt. Underneath I can see already that she is not wearing a bra.

I don’t want to undress. I know Thea would laugh at my self-consciousness, but I can’t help thinking of my post-pregnancy body, my blue-veined milky breasts, and the stretch marks on my still-soft belly. It would be different if Fatima were swimming too, but she’s not – it will be me and Thea and Kate, both of them as slim and lithe as seventeen years ago. But I know I won’t get out of it, not without a ribbing from Thea. And besides, there’s part of me that wants to. It’s not just the stickiness of the hair against my neck, and the way my dress is clinging to the perspiration on my back. It’s more than that. We are here, all of us. There’s part of me that wants to relive that.

I take a towel and walk outside into the darkness. I never had the courage to go in first, when we were teenagers. I don’t know why not – some strange superstition, a fear of what might be lurking in the waters. If the others were there, I would be safe. It was always Kate or Thea who led the charge, usually running off the jetty with a shriek to dive-bomb into the centre of the Reach, where the current ran fast. Now, I am too cowardly not to go first.

My dress is soft, stretchy cotton and I peel it off in a single movement and drop it to one side, unhook my bra, and step out of my knickers. Then I draw a breath, and lower myself into the water – quickly, before the others have time to come out and see my soft nakedness.

‘Whoa, Isa’s gone in!’ I hear from inside, as I surface, spluttering with the cold. The night is warm, sweaty even, but the tide is high and the Reach is salt water, straight from the Channel.

Thea strolls out onto the jetty as I tread water, gasping as my skin acclimatises. She is naked, and I see for the first time that her body has changed too, as drastically as mine in some ways. She was always thin, but now she must be close to anorexia, her stomach hollow, her breasts shallow saucers against visible ribs. One thing has not changed though – her complete unselfconsciousness as she saunters to the very edge of the platform, the lamplight casting a tall slim shadow over the waters. Thea has never been ashamed of nakedness.

‘Out of my way, bitches,’ she says, and then she dives, a perfect dive, long and shallow. It’s also suicidally stupid. The Reach is not that deep, and is full of obstructions – pikes in the riverbed, the vestige of old jetties and mooring posts, lobster pots, junk washed downstream by the current, sandbanks that shift and change with the tides and the passing years. She could easily have broken her neck, and on the jetty I see Kate wince with horror, and put her hands to her mouth – but then Thea surfaces, shaking the water off her hair like a dog.

‘What are you waiting for?’ she calls to Kate, who lets out a long slow breath of relief.

‘You idiot,’ she says, something close to anger in her voice. ‘There’s a sandbank in the middle there, you could have killed yourself.’

‘But I didn’t,’ Thea says. She is panting with the cold, her eyes bright. Her arm, as she raises it from the water to beckon to Kate, is rough with goosebumps. ‘Come on, get in the sea, woman.’

Kate hesitates … and for a minute, I think perhaps I know what she is thinking. There is a picture in my mind’s eye … a shallow pit, filling up with water, the sandy sides crumbling away … Then she straightens her spine, an unconscious defiance in every bone.

‘All right.’ She peels off her vest top, steps out of her jeans, and turns to unhook her bra and then, last, before she enters the water, she picks up the bottle of wine she has brought out onto the jetty and takes a long, gulping draught. There is something about the tilt of her head and the movement of her throat that is unbearably young and vulnerable, and just for a moment the years slip away and she is the same Kate, sitting out on the fire escape at Salten House, throwing back her head to drain the whiskey bottle.

Then she lets the bottle drop on top of her pile of clothes, squares herself for the plunge, and I feel the ripples as she hits the water, feet away from me, and sinks beneath the moon-dappled surface.

I wait, expecting her to come up somewhere close … but she doesn’t. There are no bubbles, and it’s impossible to see where she is, the moonlight reflecting off the water makes it hard to see anything beneath.

‘Kate?’ I say, treading water, feeling my anxiety rise as the seconds tick past and there is still no sign of her. And then, ‘Thea, where the hell’s Kate?’

And then I feel something catch on my ankle, a cold, strong grip that jerks me down, deep, deep into the Reach. I catch a breath before I go under, but I am deep below before I can scream, grappling the thing that is pulling me down.

Just as suddenly, it lets go, and I surface, gasping and raking salt water out of my eyes, to find Kate’s grinning face next to mine, her arms holding me up.

‘You bitch!’ I gasp, not sure if I want to hug her or drown her. ‘You could have warned me!’