The light is fading faster now, turning the water a murky grey. It’s time I went back to the house.

‘Lisa? Are you all right?’

I look up. Isobel is standing at the door, her face almost translucent in the fading winter light.

‘Yes, I’m feeling much better,’ I say as I reach the house. ‘Just needed some air, that’s all.’

‘I understand,’ she says, smiling. ‘Though you must be freezing.’

She puts her hand on my arm and guides me back into the house which, in my absence, has been transformed. Warm, woody air envelops me as I step inside and my skin tingles. The fire has been lit in the living-room grate and Joe is lying on his belly in front of it, playing with the toy animals I hurriedly packed into my bag when we left London. I stand in the doorway, still shivering but unable to take my eyes off my little boy. He looks so contented and settled. Isobel has combed his hair and his face is pink and scrubbed clean. As I stand there listening to him making lion roars, lost in his play, the dark feeling returns, the sense that I have let my child down in the worst possible way; that being a mother, no matter how much I want it, will always be beyond me, just out of reach.

‘I should have combed your hair,’ I whisper.

At this, Joe looks up and sees me standing there. He gathers his animals into his arms, as though worried I’m going to take them away, then he scowls and turns his back on me. A tear escapes from my eye but I swiftly wipe it away. Joe mustn’t see me crying.

‘I found these in the kitchen.’

I turn to see Isobel standing behind me. She’s holding a pile of clothes.

‘Old jumpers,’ she says briskly. ‘They don’t look that stylish but they’re warm at least. Why don’t you get changed and I’ll keep an eye on Joe.’

I take the jumpers, like an obedient schoolgirl, and make my way down the passageway to the bedroom. Isobel has been busy making the bed and folding Joe’s clothes into neat piles. As I peel off my thin cotton top, deep sadness permeates my bones. Why can’t I be a good mother? Why am I always messing up?

When I get back to the living room I find Isobel sitting on the rug with Joe. He’s waving a toy lion at her and she screams in mock terror. ‘Save me, save me, Joe! Don’t let him eat me.’

Joe giggles and does it again. His laughter is so natural, so innocent, it physically hurts to hear. Standing in the doorway, I clear my throat and they look up at me.

‘Here’s Mummy,’ says Isobel, getting to her feet. ‘Hey, I bet that feels warmer. Tell you what, if you give me your other clothes I’ll take them back and give them a wash in my machine.’