If I’m not mistaken, he’s ordered her not to share it with me, whatever it is. It’s kind of appropriate; an enormous black room is the perfect place to be when you find out you’re about to be kept in the dark.

‘What else?’ Charlie asks Simon. ‘You said two things.’ There’s a long silence while she listens. Eventually she says, ‘Okay. It was him, ringing up about himself? I suppose that must happen from time to time. I will, now. So when did this happen? What? Well, fuck you too! That’s just perfect, isn’t it? For fuck’s sake!’

I try not to look surprised. What’s happened? Seconds later, I realise it’s obvious. Marriage is what’s happened: unnatural proximity to another human being over a prolonged period. It’s bound to be the world’s leading cause of Sudden Violent Swearing Syndrome.

‘Do you think I’m having fun driving up and down bloody motorways all day?’ Charlie rants. ‘Do you think my lungs enjoy collecting diesel fumes? What? Oh. Right.’ She sounds a different kind of annoyed now. I recognise this mode too: fuming at the prospect of having to apologise to someone you know to be guilty in general, if not on this particular occasion. ‘Whatever.’ She sighs. ‘I’d still have appreciated being told.’

She stuffs her phone back in her pocket. ‘We’ve got a name. The man who gave you the book: Niall Greeves. He rang up yesterday. Thanks to an administrative cock-up at his workplace, it’s taken Simon until today to verify that he’s legit.’ Charlie shakes her head. ‘I only want to know as much as everyone else knows or doesn’t know – is that too much to ask?’

‘They’re The Detectives, capital T capital D,’ I say. ‘You’re not. They’re going to take every chance they get to pull rank – even, especially, the one you’re married to.’

‘I used to be a detective. I used to lead that team! I was Simon’s boss.’

‘So now it’s payback time, right? Look no further for an explanation!’ I definitely shouldn’t ever go into marriage guidance counselling.

Charlie curls her lip. I imagine there are plenty more swearwords tucked inside it, waiting to be fired later, when she and her beloved are reunited. ‘Come on, let’s make a move,’ she says. ‘I’ll fill you in on the way.’

‘To where?’ I ask. As far as I’m aware, we haven’t decided where we’re going next.

‘Canterbury. That’s where it was.’ Charlie grins at me. ‘Niall Greeves has saved us days of driving.’

I ought to be pleased, given how much I didn’t want to come on this trip, but all I can think is Please let Niall Greeves be wrong. I don’t want to have to go home.