That evening, Matt announces that he wants to see if he can find a little family hotel-restaurant he remembers, off the beaten track. If it’s still there, he says, it has the most amazing pizzas. He seems suddenly obsessed with finding this place, as if it really matters to him, and I’m afraid to ask why.

We set off with a map. We’re venturing far from Piazza San Marco and we soon leave behind the main tourist routes and find ourselves twisting and turning through a maze of increasingly narrow side streets. At times, these give way without warning to hidden squares, built round modest churches with low lights.

We enter a series of paths along the edges of minor canals that are so gloomy that I call you back and make you hold my hand. The water here smells stagnant and forbidding, its surface barely visible in the darkness. I draw you away from the edge, frightened that if we fell in, we’d simply disappear into nothingness.

There are few streetlights in this forgotten stretch and the buildings look decayed and deserted. Arches and doorways are toothless with missing bricks and bowed by the weight of history. Matt walks on with purpose but his map is useless in the darkness.

Finally we emerge, as if by miracle, into a small piazza. A typical Venetian campo, Matt says, looking round as he gets his bearings. He’s clearly delighted and leads the way with renewed confidence to a tall, narrow house on its edge. It’s barely identifiable as a hotel. It looks dilapidated and cramped but full of character.

Downstairs, restaurant tables spill out onto the pavement. A middle-aged woman, prematurely thick around the waist, sits smoking at a corner table, reading a newspaper. Matt leaves us and crosses to greet her.

She raises her eyes with little interest at first, then feeling floods into her face and she jumps up, kisses him on both cheeks and embarks on an animated flow of Italian. Her eyes shine but her expression becomes wistful as she talks.

After a while, he gestures towards us and she looks over fleetingly at me, then more closely at you, pressed against my side. Her eyes are curious but I see none of the warmth in them with which she greeted Matt.

He comes back to claim us and steer us to a table.

‘Sorry,’ he says, smiling. ‘La patrona. I wondered if she’d still be here.’

I think of his student friend, Maria-Eletta, and wonder if there’s a connection here that he’s politely omitting to mention.

‘She certainly remembered you.’

He is already leaning over the pizza menu. The woman has picked up her newspaper and retreated inside, leaving us alone. A much younger woman takes our order.

Matt is suddenly subdued and I sit quietly beside him, wondering why. The pharmacy on the corner is still open and every now and then a bell jangles as the door closes on customers. Dusk deepens around us. A wrought-iron streetlight, holding three ornate lanterns, casts lengthy shadows across the paving stones.

You sit with us while we all eat, folding the edges of your pizza slices into curves, delighting in being allowed to eat with your hands.

When you’ve had enough, you jump down from your chair and, while Matt and I linger over our wine, you make your own game of hopping and skipping across the campo’s flagstones. You buzz with life and, as I watch you, a lithe figure in your buttoned-up coat, I think back to the painting we saw together, to its twisting tunnel of light and the naked figures reaching for the perfect brightness ahead.

Matt leans closer and reaches an arm round me. ‘I’m sorry. I’ve been lousy company tonight.’

I take his hand between my own. ‘Are you OK?’

He nods and draws me closer to him. His body is firm and warm against mine and I’m comforted by it but still uneasy. Something about this place, about talking with that woman, dampened his mood and I don’t understand why.

‘You were upset, weren’t you, this afternoon?’

I hesitate. His tone is sympathetic and I want to respond to it, to talk about you and your strange reaction to the painting but I’m also reluctant to change the subject and move on.

‘She was so struck by that painting,’ I say, remembering the emotion in your face. ‘Maybe she’s right. Maybe the artist did go through something similar.’

‘Maybe he did.’ Matt shrugs. ‘Experiences like that, however you explain them, must have been around for centuries. We might call them near-death experiences. Maybe they just called them visions.’

‘When did you say it was painted?’

He pauses. ‘About fifteen ten. A superstitious age. They all painted religious stuff.’

I don’t answer. Your light, high voice drifts across the campo on the breeze. You’re chattering to yourself, lost in your own world. Your hair flies round your head as you leap in and out of the shafts of light thrown across the paving stones by the lanterns, jumping between light and darkness, light and darkness. I have a strange sense of you jumping also in time, back and forth through the thin, shifting veil between past and present, between this world and the next.

Mist is gathering along the far side of the campo, rising from the canal, creeping in from the Lagoon. It blurs the edges of buildings there and swallows the shops beyond the canal.

You run back to me. Your eyes shine with the excitement of being outside so late.

‘Is it night-time, Mummy?’

‘It’s very late, my love.’

‘It’s dark!’

I just nod, reach out a hand and tickle the back of your neck. You have a habit of stating the obvious sometimes, as if you just enjoy the pleasure of making conversation.

‘Soon,’ I say, ‘we’ll go back to the hotel and then it’s straight to bed.’

You skip off again. This time you head towards a narrow hump-backed bridge over the canal in the far corner of the campo. It is already becoming engulfed by swirling mist. I narrow my eyes and struggle to keep you in sight.

Your voice drifts clearly through the still air. One. Two. Three. You count the stone steps up one side of the bridge, run back and forth across the top, then come back again, springing off the bottom step with a bound.

‘This time tomorrow,’ I say, ‘we’ll be back in London.’ It seems impossible.

Matt pulls me closer. When I encircle him with my arms, his back is broad and strong.

He kisses my cheek. ‘I don’t want it to end.’

You start to climb the steps again, this time hopping with your feet together. I hold my breath as you reach the top of the bridge and, for a second or two, disappear into the hanging fog, only to reappear again.

An Italian couple, strolling by, call out to friends and stop to talk. The song of their voices, the lilting music of their words, washes over us.

Matt lowers his voice. ‘It works, Jen. You and me. Don’t you think? And Gracie too.’

I nod. It’s been a happy weekend. For the first time, I’ve had glimpses of the three of us as a unit. As a family.

He clears his throat. ‘I know it hasn’t been very long.’

Part of me wants him to stop there, to leave things as they are and not risk spoiling them. Another part wants him to carry on.

‘I love you, Jen. You know that, don’t you? We belong together, you and me. I sensed it the first time we met.’

He cups my chin with his hand and turns my face away from you to him. His lips close for a moment on mine, stopping my breath.

‘I don’t want to rush you.’ His eyes loom large, streaked with low light. ‘But I want to take things a step further. Will you think about it? I want to look after you. You and Gracie. I want to wake up with you every morning, not creep out of the house at night as if we don’t really belong to each other.’

I pull a little apart from him.

‘Jen? What is it?’ His voice is gentle. ‘Is it too soon?’

I shake my head. ‘It should be,’ I say. ‘How long have we known each other? A matter of weeks. That’s no time at all.’ I hesitate. ‘But that’s not how it feels.’

‘How does it feel?’

‘Like a dream,’ I say, in a low voice. ‘If you’d told me a few months ago that I’d be sitting here in Venice with a doctor, talking about being together—’ I broke off.

‘Think about it. Please.’

He moves in and kisses me.

‘I love you so much, Jen. I don’t know how I’d carry on without you.’

I close my eyes.

When I open them again and look round, you’re standing on the curved back of the bridge, barely visible in the thickening mist: a slight, shadowy figure leaning forward over the wall and peering down into the canal.

I look more closely, then pull away from Matt and sit up straight.

‘Is there—’

The fog swims round you, at times obscuring you, at others giving you back to me. I get to my feet. My heart pounds. It may be no more than streaks of light shimmering in the mist but it seems to me, as I gaze, that there’s something or someone beside you, a presence even slighter than your own, there at your side. I blink, straining forward to get a better look.

‘Is that someone with her?’

Matt doesn’t seem to hear me at first. Then he understands and says: ‘With Gracie?’ He too sits straighter, cranes forward. ‘I can’t tell.’

‘Can’t you?’

I push past the table and stride towards you. I am suddenly afraid, gripped by the same fear that chilled me this morning on the boat and again as I stood high on the bell tower, looking out across the vast expanse of the Lagoon, and thought you gone.

I quicken my pace. The fog deepens and you are lost for a moment. Then I hear it. A stifled giggle drifts across the campo towards me. It is followed a moment later by the soft, light breathing of a child. The same sounds I heard so clearly as I raced up the bell tower.

The mists sway and thin in the breeze and you emerge again, leaning away from me now, over the far wall of the bridge. I shiver and run towards you. As I draw near, I catch the low murmur of voices.

‘Gracie?’

You look up, alarmed, and shout at once: ‘No, Mummy. Go away!’

You stand squarely on the narrow bridge, guarding it from me. I try to peer past you, into the darkness.

‘Come away now. It’s late.’

You stamp your foot, furious. ‘No! You’re spoiling everything.’

‘What?’ I’ve almost reached you now, my arms open, but as I move to embrace you, you pull away. ‘What’s wrong?’

‘You made her go away.’ You hit out at me, arms flailing. ‘Why, Mummy? Why did you do that?’

‘Calm down, Gracie!’ I try again to hold you but you lash out and struggle, barely able to contain your rage. ‘It’s alright.’

‘It’s not alright.’ Your face crumples, close to tears. ‘She was here and you’ve frightened her away.’

‘Who?’

‘Catherine.’

‘Gracie.’ I shake my head. As I look past you, all I see is a wall of dense fog, streaked with light bouncing off the fast-moving water below. ‘It’s very late.’

You lean over, peer down at the black stream gliding through the darkness. Your pale face, reflected there, shimmers.

‘We need to go.’ I hold out my hand for you to take. ‘Come on.’

You burst into sobs, fall to the ground and bang your fists, your feet.

I stand, helpless, watching you.

‘Gracie. Sweetheart. Get up.’

I lean over you, lifting your shoulders even as you struggle against me, trying to pull you to your feet.

‘No, Mummy. You don’t understand. She’s gone again. It’s your fault. Why did you come? Why?’

I can’t answer. I manage to hoist you up into my arms, battling to contain you as you scream and kick and shout: ‘No! No!’

I carry you down off the bridge, away from the water and back onto solid ground. As we cross the campo towards him, Matt stands motionless, watching us approach, his face pale.