‘Slow down. Supposing he did go down to Devon, how did he get there? His car is parked in your driveway and there’s no CCTV footage of him beyond the Queen’s Arms. The Paddington station sighting wasn’t him.’

‘I don’t know. But it’s not impossible, is it? Maybe he hitched a lift. Please can you at least look at it?’

He gives in. ‘I’ll talk to Devon and Cornwall Police for you, but don’t expect them to organize a search without a very good reason.’

It’s something. I’ve driven a small wedge in the door. I risk another push.

‘I think Nick was so upset by meeting Anna Foreman and her brother, and the memories that triggered, that he may have harmed himself or be intending to.’ A lump rises in my throat, causing a break in my voice.

‘Has he ever given you reason to believe he’s capable of something like that?’

Once upon a time I would have said absolutely not, but now I know about his depression, I’ve had to rethink our entire relationship. ‘It can happen to anyone, surely? Given the right set of circumstances.’

He is unimpressed. ‘If we assigned officers to every what if, we wouldn’t have time to deal with the crimes that are actually being committed. We haven’t been sitting on our hands. We’ve uploaded Nick’s details on to the Missing Persons database. We’ve looked at his computers both at work and at home. We’ve spoken to his colleagues. We’ve been through his phone records and his bank and credit card statements. I have a list as long as my arm of things that need my attention and people who need my help. I cannot devote every hour of every day to finding Nick. If he wanted to go back there to kill himself, why not drive, or get the train?’

‘Because he didn’t want to be found.’

I can almost hear the lift of his eyebrow. I can certainly picture it.

‘My point exactly.’

Cornered, I groan. ‘It’s not that simple.’

‘Ms Trelawney.’ He sounds exasperated. ‘If you know something, you should tell me, even if it doesn’t show Nick in the best light. If what you’re saying is true, then we need to act quickly.’

What Anna told me – what she implied about Nick and Izzy’s relationship becoming blurred around the edges – is hard to articulate, because it goes against everything I know about Nick. I could repeat it to Marsh, but the slightest suggestion that a sixteen-year-old boy assaulted a thirteen-year-old girl, and possibly has some indirect connection to her death, has implications that could be life-changing and career-destroying.

‘I’ve told you everything I know.’

‘OK,’ he says after a pause. ‘I’ll talk to Moody again.’

‘And the Wellses. You need to talk to Anna’s parents.’

He sighs.