Hamish’s parents had gone off on holiday, to stay with friends in a rented house in the Dordogne, taking his sister with them. He had the house to himself. He didn’t arrange the party until they’d been gone for three days, just to be on the safe side. Last year they’d left their passports and traveller’s cheques in the kitchen and had had to turn around and come back for them. Luckily he’d only had a couple of friends over that time, but he didn’t want to risk his family appearing this year, when he’d invited loads of people.

Stephen had driven Cass and Georgie over in Nick’s car. Cass had been in her sunniest mood, her feet up on the dashboard. Georgie sat directly behind him, occasionally snaking her right arm around the outside of the driver’s seat so her sister wouldn’t see, to stroke his shoulder. Since the night she’d come to his room, they’d been sleeping together in his narrow bed. After the second time, she had confided that she’d thought she was going to be one of those people who don’t really like sex. But now she did.

‘I was going to experiment on you,’ she said.

‘So I was just a guinea pig?’

‘Yes. Pretty much. I thought if it went badly at least I wouldn’t have to see you every day afterwards, at school.’

‘Oh. Thanks for that,’ he said, stung.

But she didn’t notice. ‘It’s my pleasure,’ she said, smiling.

Being so delighted to learn that she wasn’t condemned after all to a life of celibacy made her adventurous: she did things that no girl Stephen had been with had done before. Not that there’d been so very many: two girls back home and one New Zealander in a youth hostel in London, before Helena. But this was different, freer. There wasn’t an inch of him that Georgie hadn’t tasted; the back of his neck, his underarms, even his bum. She’d giggle as she manoeuvred their limbs into new positions, as if they were giant dolls. ‘Let’s try it like this,’ she’d say.

It made him fancy her more than he’d ever fancied anyone. Every minute that they weren’t entwined he now imagined her, imagined them together. But he still held a torch to Cass, he just couldn’t help it. Georgie was more alive than her sister, more daring: he guessed that Cass would be much more passive in bed. But he couldn’t stop himself loving her, reserved as she was and slightly serious and to him infinitely tender. He felt protective of her in a way that he’d only experienced towards his kid sisters. He knew it was hopeless, he wasn’t stupid. But still he couldn’t switch off the tap of his heart.