I’ve left Freya with Owen a few times. But never like this – never with someone I don’t know from Adam.

What if something happens?

‘Give me the numbers,’ I say to Kate again, ignoring Fatima, shrugging her hand off my shoulder, and I pick Freya up and we go upstairs, the list of numbers clutched in my hot fist, trying not to give way to tears.

IT IS LATE. The sun is dipping in the sky, the shadows over the Reach are lengthening, and Freya is nodding at my breast, her hand still clutched around the fragile necklace of twisted silver wire that I rarely wear any more, for fear she’ll tug it and snap the links.

I can hear the others conversing downstairs. They’ve been ready for ages, while I try and fail to get Freya to sleep. But she’s picked up on my nerves, wrinkled her face disgustedly at the unaccustomed smell of the perfume I’ve dabbed behind my ears, batted angry hands at the slippery black silk of a too-tight sheath dress borrowed from Kate. Everything is wrong – the strange room, the strange cot, the light slanting through the too-thin curtains.

Every time I lower her to the mattress of the cot she jumps and flails and snatches at me, her angry wail rising like a siren above the noise of the river and the low voices downstairs.

But now … now she seems really and truly asleep, her mouth gaping, a little trickle of milk oozing from the side of her lips.

I catch it with the muslin before it can stain the borrowed dress, and then rise, very stealthily, and edge my way to the cot in the corner.

Lower … lower … I bend over, feeling my back twinge and complain, and then at last she’s on the mattress, my hand firm on her belly, trying to merge the moment of my being there into the moment of my not being there so smoothly that it passes unnoticed.

Eventually I stand, holding my breath.

‘Isa!’ comes a whispered hiss up the stairs, and I grit my teeth, screaming shut up! inside my head, but not daring to say it.

But Freya slumbers on, and I tiptoe as silently as possible towards the corridor, and down the rickety stairs, my finger to my lips as the others raise a muted cheer, and then hastily hush at the sight of my face.

They are standing, huddled together at the bottom of the stairs, their eyes upturned to mine. Fatima is dressed in a stunningly beautiful jewelled shalwar kameez in ruby silk that she somehow found in a formal-wear shop in Hampton’s Lee this afternoon. Thea has refused to bow to the dictates of the black-tie invitation and is wearing her usual skinny jeans and a spaghetti-strap top that starts out gold at the bottom hem, and deepens into midnight black at the neck, and it reminds me so much of the hair she used to have as a girl that my breath catches in my throat. Kate is wearing a rose-pink handkerchief dress that looks like it could have cost either pence, or hundreds of pounds, and her hair is loose around her shoulders and damp from the shower.

There is a lump in my throat as I come to the foot of the stairs – and I don’t even know why. Perhaps it’s the sudden, heart-shattering realisation of how much I love them, or the way they have grown from girls to women in the space of a heartbeat. Perhaps it’s the way their faces in the evening sunlight are overlaid by the memory of the girls they once were – they are polished, a little wary, eyes a little tired, but more beautiful than I ever remember them being as girls, and yet at the same time they are clear-skinned, hopeful, poised like birds to take flight into an unknown future.

I think of Luc, and his anger in the shop, the veiled threats, and I feel a sudden clenching fury – I cannot bear for them to be hurt. Any of them.

‘Ready?’ Kate says with a smile, but before I can nod, there is a cough in the corner, and I turn to see Liz, the girl from the village who has come to take care of Freya, standing by the dresser.

She is horrifyingly young – that was the first thing I thought when she arrived, knocking on the door with a tentative rap. She said on the phone she was sixteen but I don’t know if I believe it now I’ve seen her – and she has pale brown hair and a broad, blank face that is hard to read, but looks anxious.

Thea looks at her phone. ‘We need to go.’

‘Wait,’ I say, and I begin again the speech that I’ve run through twice already – the cup of expressed milk in the fridge, the comforter she doesn’t like but I keep hoping she’ll take to, where the nappies are, what to do if she won’t settle.

‘You’ve got my number,’ I say for maybe the twentieth time, as Fatima shifts from one foot to the other and Thea sighs. ‘Right?’

‘Right here.’ Liz pats the pad on the dresser, next to the pile of tenners that is her fee for the night.

‘And the milk in the fridge – I don’t know if she’ll take it – she’s not very used to sippy cups – but it’s worth a try if she wakes up.’

‘Don’t worry, Miss.’ Her small eyes are a guileless blue. ‘My ma always says there’s no one to beat me with my little brother. I look after him all the time.’

This doesn’t really reassure me, but I nod.

‘Come on, Isa,’ Thea says impatiently. She is standing at the door, her hand on the latch. ‘We’ve really got to get going.’

‘OK.’ I feel the wrongness of what I’m doing twist at my gut as I walk towards the door, but what choice do I have? The distance between me and Freya stretches, like a cord around my throat tightening as I pull away. ‘I’m going to try to duck out early, but call me, OK?’ I say to Liz, and she nods, and I’m peeling myself away from her, from Freya, every step making a hollow place inside my chest.

And then I’m across the rickety wooden bridge, feeling the even-ing sunlight on my back, and the emptiness lifts a little.

‘So I guess I’m driving …?’ Fatima says, getting out her keys.

Kate looks at her watch.

‘I don’t know. It’s ten miles round by the road and we’re very likely to hit a tractor at this time. They’re all working late on the fields in this weather, and there’s only one route they can take. If we get stuck behind one we could be there for ages.’

‘So, what?’ Fatima looks almost comically horrified. ‘Are you saying we should walk?’

‘It’d probably be quicker. It’s only a couple of miles if we cut across the marsh.’

‘But I’m wearing evening shoes!’

‘So change into your Birkenstocks.’ Kate nods at Fatima’s shoes, left neatly outside the door. ‘But it’ll be easy walking. It’s dry in this weather.’

‘Come on,’ Thea says, surprising me. ‘It’ll be like old times. And anyway, you know what parking will be like at the school. We’ll get boxed in, and you won’t be able to get the car out until all the other rows have left.’

It’s that suggestion that swings it. I can see in Fatima’s eyes that she is as reluctant as the rest of us to be stuck at school, unable to get away. She rolls her eyes, but kicks off her shoes and pushes her feet into her Birkenstocks. I switch my heels for the sandals I wore to walk to the village, wincing slightly as they rub the same sore places from the long walk. Kate is already wearing low, sensible flats, and so is Thea – she doesn’t need the extra height.

I give one last look at the window where Freya is sleeping, feeling the painful tug. And then I turn my face towards the track, south, towards the coast, and I take a deep breath.

Then we set off.

It is like old times, that’s what I think as we walk down the same track we always used to take back to Salten House. It is a pure, beautiful evening, the sky streaked with pink clouds reflecting the setting sun, the sandy track giving back the day’s warmth to our feet.

But we are only halfway along the shore path when Kate stops abruptly and says, ‘Let’s cut through here.’

For a minute I can’t even see where she means – and then I see it – a gap in the tangled, thorny hedge, a broken-down stile just visible among the nettles and brambles.

‘What?’ Thea gives a short laugh. ‘You joking?’

‘I –’ Kate’s face is uncomfortable. ‘I just thought … it’ll be quicker.’

‘No it won’t.’ Fatima’s face, behind her outsize black shades, is puzzled. ‘You know it won’t – it’s a less direct route, and anyway, there’s no way I can get through there, it’ll rip my outfit to shreds. What’s wrong with the stile further down? The one we always used to take back to school?’