The soft, saggy sofa sighs as Luc climbs onto it, and I lie back and he takes me in his arms, and I feel his weight against me. My lips are on his throat, feeling the tenderness of the skin between my teeth, and tasting the salt of his sweat … and then suddenly I freeze.

For there, in the shadows at the top of the staircase, something is moving. A figure in the darkness.

Luc stops, raises himself up on his arms, feeling the sudden tense stillness of my muscles.

‘Isa? Are you OK?’

I can’t speak. My eyes are fixed on the dark space at the top of the stairs. Something – someone – is up there.

Pictures flash through my head. A gutted sheep. A bloodstained note. An envelope full of drawings from the past …

Luc turns, looks over his shoulder in the direction of my gaze.

The draught of his movement makes the lamp gutter and flare, and for a moment, just the briefest of moments, the flame illuminates the face of the person standing in the darkness, silently watching.

It is Kate.

I make a sound – not a scream, but something close to it, and Kate turns and disappears into the silent upper floors.

Luc is scrabbling his T-shirt back over his head, buttoning his jeans, leaving his belt trailing in his haste. He takes the stairs two at a time, but Kate is too quick for him. She is already halfway up the second flight and I hear the attic door slam and a key turn in a lock, and then Luc hammering at the door.

‘Kate. Kate! Let me in!’

No answer.

I begin to re-button my dress with shaking fingers and then scramble to my feet.

Luc’s feet sound on the stairs, his step slow, and his face, when he comes back into the circle of lamplight, is grim.

‘Shit.’

‘She was there?’ I whisper. ‘All the time? Why didn’t she come when we called?’

‘Fuck knows.’ He puts his hands over his face, as if he can grind away the sight of Kate standing there, her face blank and still.

‘How long was she standing there?’

‘I don’t know.’

My cheeks burn.

We sit, side by side on the sofa for a long, silent time. Luc’s face is impassive. I don’t know what my expression is like, but my thoughts are a confused jumble of emotion and suspicion and despair. What was she doing up there, spying on us like that?

I remember the moment the lamp flared, and her face – like a white mask in the darkness, eyes wide, mouth compressed as though she was trying not to cry out. It was the face of a stranger. What has happened to my friend, the woman I thought I knew?

‘I should go,’ Luc says at last, but although he gets to his feet, he doesn’t move towards the door. He just stands there, looking at me, his dark brows knitted in a frown, and the shadows beneath his wide cheekbones giving his face a gaunt, haunted look.

There is a noise from upstairs, a whimper from Freya, and I stand up, irresolute, but Luc speaks before I can.

‘Don’t stay here, Isa. It’s not safe.’

‘What?’ I stop at that, not trying to hide my shock. ‘What do you mean?’

‘This place –’ He waves a hand at the Mill, taking in the water outside, the dead light sockets, the rickety stairs. ‘But not just that – I –’

He stops, scrubs his free hand into his eyes, and then takes a deep breath.

‘I don’t want to leave you alone with her.’

‘Luc, she’s your sister.’

‘She’s not my sister, and I know you think she’s your friend, but Isa, you – you can’t trust her.’

He’s lowered his voice to a whisper, even though it’s impossible that Kate should hear us – three floors up, and behind a locked door.

I shake my head, refusing to believe it. Whatever Kate has done, whatever strain she’s under right now, she is my friend. She has been my friend for almost twenty years. I won’t – can’t – listen to Luc.

‘I don’t expect you to believe me.’ He’s speaking hurriedly now. Freya’s wail from above gets louder, and I glance at the stairs, wanting to go to her, but Luc is still holding my wrist, his grip gentle but firm. ‘But just – just please be careful, and listen, like I said, I think you should leave the Mill.’

‘I’ll leave tomorrow,’ I say it with a heaviness, thinking of Owen and what’s waiting for me back in London, but Luc shakes his head.

‘Now. Tonight.’

‘Luc, I can’t. There’s no train until the morning.’

‘Then come back to my flat. Stay the night. I’ll sleep on the sofa,’ he adds hurriedly, ‘if that’s what you want. But I don’t like to think of you here, alone.’

I’m not alone, I think. I have Kate. But I know that’s not what he means.

Freya wails again, and I make up my mind.

‘I’m not leaving tonight, Luc. I’m not dragging Freya and my luggage halfway across the marsh in the middle of the night—’

‘So get a cab –’ he cuts in, but I’m still talking, ignoring his protests.

‘—I’ll leave first thing tomorrow – I’ll catch the 8 a.m. train if you’re really worried, but there is no way that I’m in danger from Kate. I’m just not. I’ve known her for seventeen years, Luc, and I can’t believe it. I trust her.’

‘I’ve known her for longer than that,’ Luc says, so quietly that I can hardly hear him beneath Freya’s choking wails. ‘And I don’t.’

Freya’s cries are too loud for me to ignore now, and I pull my wrist gently out of his grip.

‘Goodnight, Luc.’

‘Goodnight, Isa,’ he says. He watches as I retreat up the stairs with the oil lamp, leaving him in darkness. Upstairs, I pick up Freya, feeling her hot little body convulsing with angry sobs, and in the silence that follows I hear the click of the door latch, and the sound of Luc’s footsteps on gravel as he disappears into the night.

I DON’T SLEEP that night. I lie awake, words and phrases chasing around my head. Pictures Kate said she had destroyed. Lies she has told. Owen’s face as I left. Luc’s face as he walked towards me in the soft lamplight.

I try to piece it all together – the inconsistencies and the heartbreak – but it makes no sense. And through the whole thing, like maypole dancers, weave the ghosts of the girls we used to be, their faces flashing as they loop over and under, weaving truth with lies and suspicion with memory.

Towards dawn one phrase comes into my head, as clear as if someone whispered it into my ear.

It is Luc, saying I should have chosen you.

And I wonder again … what did he mean?

It’s six thirty when Freya wakes, and we lie there, she feeding at my breast, me considering what I should do. Part of me knows I should go home to London, try to mend bridges with Owen. The longer I leave it, the harder it’s going to be to salvage what’s left of our relationship.

But I can’t face the thought, and as I lie there, watching Freya’s contented face, her eyes squeezed shut against the morning light, I try to work out why. It’s not because of what happened with Luc, or not just because of that. It’s not even because I’m angry with Owen, for I’m not any more. What happened last night has somehow lanced my fury, made me face the ways I’ve been betraying him all these years.

It’s because anything I say now will just be more lies. I can’t tell him the truth, not now, and not just because of the risk to his career and the betrayal of the others. But to do that would be to admit to him what I’ve already admitted to myself – that our relationship was built on the lies I’ve been telling myself for the past seventeen years.

I need time. Time to work out what to do, how I feel about him. How I feel about myself.

But where do I go, while I figure this out? I have friends – plenty of them – but none where I could turn up with my baby and my bags and no end for my stay in sight.

Fatima would say yes in a heartbeat, I know she would. But I can’t do that to her, in her crowded, chaotic house. For a week, maybe. Not longer.

And Thea’s rented studio flat is out of the question.

My other friends are married, with babies of their own. Their spare rooms – if they have any – are needed for grandparents and au pairs and live-in nannies.