But Mark shook his head. He brushed his hands against each other as if to say, job well done.

‘No, I’d best be off,’ he said. ‘Enjoy the books. Take care, Ava.’

‘I’ll show you out,’ I said.

I followed Mark downstairs to the lobby and let him out of the building, and then, on impulse, trotted along behind him all the way to his car.

I knew Ava would feel I’d let the side down, and I felt bad about it but not enough to change tack. If Ava was going to be mean to Mark, that was up to her. I was going to be extremely nice to him. After all… why shouldn’t I be? Who was I being disloyal to? Not Dad, who we hadn’t seen for ages. Not Mum, who was in love with Mark and wanted us to get on with him. Only Ava, who seemed to have decided to make things difficult. Like she was testing him. Why did she have to be so weird about it?

And yet…

There was something about it I didn’t really understand. Something about him.

Something he’d done, perhaps, a long time ago? Or something he ought to have done, and hadn’t?

Whatever it was, it bothered him, and it wasn’t going to go away. I’d felt it that first time we met him, when he took Ava’s hand in the car. And I could feel it now.

He didn’t seem to have noticed that I’d followed him. He pressed his key fob to unlock the car door and I said, ‘The books are really nice. I think Mum will like them, too. It was very kind of you.’

He started, and for a moment he looked almost as if I repelled him. Then he smoothed his face into a more appropriate adult-to-child expression – friendly, and slightly patronising – and said, ‘Sorry, Ellie, lost in thought.’

I shrugged. ‘It’s OK. People often forget I’m there.’ Especially when Ava’s there too. And even when she isn’t. ‘I’d probably make a brilliant spy.’

‘I’m sure you would,’ Mark said. Then: ‘Ellie, I hope you don’t mind me asking, but how much do you see of your dad?’

‘It depends,’ I said. ‘It’s been a while.’

‘When you do see him, do you get along with him?’

I hesitated. How to sum up our relationship with Dad in a sentence or two? You couldn’t just say it was awkward and leave it at that. You could say that of any relative you didn’t see very often, and with Dad it was different. It always felt like something big was still unfinished, and maybe always would be.

It was like the picture that I’d got started on in school last summer, which was going to be of the most beautiful garden in the world. I had a big piece of sugar paper to work on, and I was planning to make it perfect. But I’d only got as far as the beginning of the path and the outline of the borders, and then there’d been no more time and the picture had somehow got lost.