Patrick scrawled a line in his pad. ‘Let’s come back to that. Alice told me that her boyfriend, Larry Gould, didn’t come round that evening. Do you believe her?’

Sean said, ‘Yes,’ and Helen said, ‘No.’

‘A difference of opinion.’

Sean said, ‘She was told not to invite Larry round that evening. Why should we disbelieve her when she says she didn’t?’

‘Why did you tell her not to invite him? Don’t you like him?’

Sean laughed humourlessly. ‘I like him as much as any father likes his teenage daughter’s boyfriend.’

Patrick waited for him to say the obvious, and Sean didn’t disappoint. ‘I know what boys are like at that age.’

‘He’s actually a nice kid,’ Helen said. ‘He’s a bit rough round the edges, very “street.” But he’s always very polite and quite funny. I can understand what Alice sees in him. She’s at the age where boys who seem a little bit dangerous and different to what their parents approve of are very appealing.’

Patrick was impressed by how quickly Helen had pulled herself together. She was in that calm state of mind that people often go into after a big emotional episode.

‘So why didn’t you want him coming round while you were out?’

‘Because,’ Helen said, ‘I know what boys and girls are like at that age. I didn’t want them making loads of noise and disturbing Frankie. Maybe it’s because I’m not Alice’s natural mother, but I’m not that bothered about the thought of them having sex in her room. I mean, they’re obviously doing it anyway.’

‘What?’ Sean said, appalled.

‘Oh, come off it, Sean,’ Helen said. ‘They’ve been together six months. Of course they’re sleeping together.’

Sean looked sick and Patrick had a horrible vision of himself in thirteen years’ time, going through the same with Bonnie.

‘But despite your warning, you think Larry did come round that night?’ Patrick asked Helen.

‘I’d be amazed if they could resist. And I bet that’s what they were doing when Frankie . . . was taken.’ Her face darkened again. ‘Alice was too busy screwing her boyfriend to look after her sister.’

Sean stood up and pointed a finger at his wife. ‘Don’t talk about Alice like that. None of this is her fault.’ His face shifted from white to pink to purple before Patrick’s eyes. The truce between the Philipses was over.

‘Please,’ Patrick said. ‘Mr Philips, sit down.’ He waited till Sean had taken his seat, at the very edge of the sofa, before asking, ‘Do you know if Larry and Alice are into drugs?’

He expected the ‘yes’/’no’ conflict again, but while Helen thought about it, Sean said, ‘It wouldn’t surprise me. Like you said about the . . . sex thing, they’re teenagers, aren’t they? I’m sure they smoke a bit of dope.’