‘I think the image of the young girl your wife saw on your phone is reason enough.’ The DI speaks through gritted teeth just as there’s a knock on the door of the interview room. ‘One moment.’ After a brief exchange at the door, he comes back. ‘We’ll break for now. Ten minutes. May.’ Nodding to me, he walks out.

As soon as we’re away from the interview room, the DI starts talking. ‘We’ve found enough to implicate him in Operation Rainbow. He and Mason were in cahoots. Calder’s involved too.’

‘You’re sure, sir?’

‘A tidy sum in a bank account set up under a false name that’s been found among Mason’s records – and that he’s accessed from his laptop. He and Mason corresponded by email – Mason used a false name too. It very much looks as though they were partners.’

After all of his lies and inconsistencies, an odd sense of relief fills me that this evil man will be removed from circulation for a long time. Then I think of Elise, at last free to begin her new life without him.

*

When we return ten minutes later, the DI is icily calm and the friction in the interview room is palpable. ‘Doctor Buckley, I’m asking you for the last time if you know anything about Mason’s business.’

Sitting back and folding his arms, Buckley doesn’t miss a beat. ‘I’ve told you more than once, you’re barking up the wrong tree.’

Knowing what we now know, I realise we truly are looking at a psychopath.

The DI is silent for a while. ‘We have incontrovertible proof to the contrary, Doctor Buckley, and I am arresting you on suspicion of the production and distribution of pornographic images of children, as well as perverting the course of justice.’

‘You’re making a mistake.’ The look he gives me before he turns to his lawyer makes my blood run cold, and I’m reminded of what Elise has lived with. ‘Do something about this.’

‘There is nothing to do, Doctor Buckley.’ The DI stands up. ‘You’ve committed a crime – several, in fact. You couldn’t honestly have believed you’d get away with it?’

*

As we walk back to the DI’s office, there’s something on my mind. ‘There was something he said just now, sir. He said we were talking to the wrong person – that we needed to talk to his wife.’

‘You have – several times.’ The DI sounds impatient. ‘Don’t get drawn in by anything he says. We know he lies. In any case, we’ve ruled her out as a suspect.’