‘I didn’t. But I changed my mind.’

Mum said, ‘You won’t be too long, will you?’

‘I won’t,’ I said. Suddenly I just wanted to get away from the pair of them.

‘Go on then,’ Mum said, and I got up and went down to the water’s edge.

When I turned round they were deep in conversation. Arguing? It was difficult to tell. Mum waved, though. At least she was still keeping an eye out for me. At least if I plunged into the water and started swimming towards the horizon, out of my depth, she’d probably notice.

I didn’t, though. I paddled and looked at the light bouncing off the water and listened to the swish and rush of the waves and the wet rattle of the sand, and to my surprise I was all right. I was sad, too, the way you are when something has come to an end, whether it’s because it’s time to put away the Christmas decorations or because your favourite old dress doesn’t fit you any more. I couldn’t help but see all the time Ava and I had spent together – eating meals, walking to and from school, sleeping side by side – in a different way. It made me nostalgic. As if all that time was already over.

But still, I was weirdly comforted. There was a sort of golden glow to everything, as if the brightness all around wasn’t just the sunshine of the south of France but was also a kind of light that you might be able to find anywhere if you looked for it.

What would my grandma have made of all this, of the choices Mum had made and the way she had deceived us? Would she have disapproved? It seemed quite possible. But anyway, she wouldn’t have been angry with us. None of it was Ava’s fault. Or mine. We were just caught up in the aftermath of what the grown-ups had done.

It made sense. Now that I knew what I was looking for, I could see it. It wasn’t just the physical resemblance… it was all sorts of smaller, subtler things. Little mannerisms. Reserve. Neatness. That way both Mark and Ava had of looking at you if you asked a question. As if they had an answer ready but weren’t sure you deserved to hear it.

Would she be even more distant with me, after this?

Ava had always annoyed me and I had always admired her. She was a giant, and always had been: an unpredictable giant, neither entirely friendly nor an ogre, but always a huge, towering presence, someone who might just as well take you for a ride on her shoulders as shut out the light. She set the standards to aspire to: she was the one I had to either follow or break away from. I could try to do better than her, I could try to be different, but either way, I always needed her. Without her, I didn’t know myself.