Was that the real reason why Mark had been so keen to be part of our lives – to claim Ava? Once he knew about her, had it really all been about her – not about Mum at all?

It wasn’t that he’d been horrible to me – he’d always been perfectly nice and kind. But from his point of view, I probably just came along as part of the package. It was like when you were house-hunting, and saw somewhere with a box room that might turn out to be useful but wasn’t much of a draw in itself. I was an extra, but I didn’t matter all that much either way.

But soon there was going to be a new baby. The baby that was more Ava’s sibling than I was, even though I’d been around so much longer, and had shared a room with her, and put up with her for years. And the baby would barely even get to know Ava, because Ava was so big now and would probably have left home by the time the baby was a toddler.

That hurt. I wasn’t sure if the hurt was made up of jealousy or sadness, or both. It felt a bit like hate. How could you hate a baby that hadn’t even been born yet? But I did. It was easier than hating Ava or Mum or Mark or Dad. My dad. It wasn’t fair, but that didn’t make a lot of difference.

Then I pulled myself together and went back up onto the beach to join Mum and Mark, and Mum said we should head off and we left the beach and made our way back to Ava.

It was a beautiful walk, along a promenade and up a path past shuttered white houses with great boughs of brightly coloured flowers spilling over their walls, just like in the pictures of the town in the hotel brochure. I asked Mum what it was called and she said it was bougainvillea. It was all so pretty that it should have been impossible for us to be anything but happy.

The path rose steeply, and the sun was at our backs. In a minute we’d come out onto the busy main road that led to the hotel, and then we’d have to find Ava, and then we’d probably all have a rather awkward lunch together and begin the business of getting used to each other again.

It was then that I saw it, on the ground alongside us.

A fourth shadow. Not so long as mine. The shadow of a girl, a little girl, a girl who wasn’t really there.

Mum was oblivious. She was looking at the sky, the flowers, the passing buildings – anywhere but at her feet. Mark didn’t look as if he’d seen it, either. He had the focused, uncomfortable expression that I’d seen on other kids’ faces at sports days, when they were tired out but the end of the race was in sight and there was no question of giving up.