This can’t be me. I don’t cry. I’m scared I won’t survive this, and even more scared I will and I’ll die of shame. At the moment, I feel nothing but a need to cling on.

‘I think water would be a good idea,’ says Charlie quietly. ‘Why don’t you try to get up and come with me to the bathroom?’

‘No. I can’t move.’ My heart’s beating too fast but the beats are wrong: each one hurts, like a big ball being forced through a hole that’s too small. ‘Tell me … something.’

‘What?’

‘Anything. A story. An old case. Anything.’ Something I can concentrate on that isn’t sad. The tears have stopped and I’ve started to shake. It makes it difficult to speak.

‘How about a mystery?’

‘Yes,’ I whisper.

‘Okay,’ says Charlie. ‘I’m going to tell you a story about my sister Olivia.’

‘You’ve got to find out,’ I say once we’re back on track after a wrong turn on the way out of St Albans. Next stop is Watford Colosseum. ‘If it was my brother, or even an acquaintance, I’d have to know.’

‘Simon thinks I should stop obsessing,’ she says. ‘Advice I’ve never heard him give before. I think I’ve finally made him realise how boring someone else’s obsession can be.’

‘I wouldn’t call it obsession, I’d call it due process.’

‘How so?’

‘If someone significantly deceives you and they’re not clever enough to conceal their lie, you’re entitled to go after them with the full force of your snooping capacity.’

‘Yes! Exactly. That’s how I feel.’

‘Snoop and be proud.’ As I say this, the driver of a car we’re overtaking turns and stares long and hard at me, as if encouraged by my words, though he couldn’t possibly have heard them. He grins and waves. I turn away pointedly. ‘I think I just saw Kim Tribbeck,’ he’ll be saying to his passengers now, and they’ll be asking him if he’s sure, or saying, ‘So what?’ or ‘Who’s she?’

‘The one thing I can’t see a way to do is get into Liv’s Gmail account,’ says Charlie. ‘That’s really all I’d need. Whatever’s going on, she’ll be corresponding with someone about it – Nikhil and Natalie, probably. I can’t risk it, though. It’s unambiguously illegal. I’d need to enlist someone at work to help me, and then we’re talking criminal conspiracy.’

‘You can’t guess her password?’

‘I’ve tried more than a hundred guesses.’

‘So you only mind the illegal part if there’s a witness? It’s okay, I get it. I’d be the same.’