She catches herself. ‘Oh yes, I was, wasn’t I?’ She explains why, how Nevis would call her text abbreviations OPT, for old person text. ‘She’s always on at me to use predictive text.’

There’s a pause. Outside the country slides by.

‘I’m glad you’re feeling better,’ Alex says finally.

‘I’m not, not really.’

‘It’s still nearly another hour to Bristol,’ he says.

How to explain that all of this has stirred up in her a wayward, almost savage desire for revenge. It burns in her, white hot and rageful as a wildfire. She closes her eyes and takes a deep breath. In nearly twenty years she has never told anyone the whole story. There never will be a good time, she knows that, but there might not be a better time either. Steeling herself, she begins:

‘When I was Nevis’s age, I had this friend, Zoe. She was the only real friend I’d ever had. We met as students studying classics at St Olaf’s. We loved each other, Alex, I mean really loved each other. Zoe was the sister I never had.’ She swallows hard, pushing down the grief.

‘Nevis’s birth mother?’

‘Yes. When we were in our second year, the university let in a mathematics prodigy, Christopher Mulholland…’

‘…the guy Gary was talking about?’

‘The same. Really young he was, like fifteen or sixteen, brilliant but still a minor, so his mother came with him. He was obviously completely under her thumb. She used to humiliate him in public. It was horrible, really. Anyway, most students just ignored Christopher but there were some who teased him mercilessly, bullying, I guess. And there was this group who sort of took him as their mascot. They were mean actually, but either he didn’t care or he was so desperate to fit in that he took it. Zoe was on the edge of this group, but she was kind to him and paid him attention because Zoe was like that. Maybe it was inevitable, given how lonely he was, but he developed this terrible crush on Zoe. She had no interest in him sexually – to us he was still a kid. Everyone except me thought it was funny, you know, laughable, even sweet. But I saw the way he used to look at her, the way he would pierce her with his eyes. To me there was something off about him, something creepy.