There was a knock on the door. Polly immediately leaned forward and grabbed the photographs, just as it opened.

Ned Watkins peered in. He shot a ‘still here?’ look at the detectives, then addressed his wife coldly again. ‘Off to poker – everything OK?’

‘Fine,’ she said. ‘I’m going to my kick-boxing class shortly.’

‘See you,’ he said.

‘See you,’ she replied stiffly.

As he closed the door, the lack of affection between the two hung in the air like the vapour from dry ice.

‘Mrs Watkins,’ Grace asked, ‘where were you last Sunday, September the first, around 5.30 p.m.?’

‘I took our dog, Kiko, for a walk on the Dyke.’

‘Is that all?’ Grace persisted.

Outside they heard the roar of a high-powered engine starting, followed by what seemed to the officers to be several unnecessarily loud revs, as if Ned Watkins was signalling some displeasure. Then came a squeal of tyres and the vroom of the McLaren, they presumed, roaring off at speed.

Seemingly ignoring the sound, Rebecca Watkins gave Grace a long, hard stare. ‘I’m guessing you know the answer to that. So, before I say anything else, am I a suspect – is that what this is about? Should I have my solicitor present?’

Both detectives shook their heads. ‘No, you are not a suspect,’ Grace answered. ‘Not at this moment.’

‘Meaning?’ she rounded on him.

‘If you were a suspect, we would have arrested you,’ Grace said. ‘We are aware that you appear to be in some form of relationship with Niall Paternoster, who is a person of interest to us. The purpose of coming to see you is to be able to eliminate you from our enquiries.’

‘Or implicate me?’

Roy Grace stared levelly at her. ‘We need to make sure you didn’t help Niall Paternoster murder his wife, Eden, and dispose of her body.’

‘That’s absolutely ridiculous!’ she replied.

‘Then you have nothing to worry about. We would like you to come to the Police HQ in Lewes tomorrow morning to be interviewed as you are an important witness. What time would be convenient?’

‘I’m in a meeting at work all tomorrow morning – it’s the monthly appraisals of my team, we’re having to do them on a Saturday.’

‘Fine,’ Grace said. ‘What about tomorrow afternoon?’

She shook her head. ‘I’ve meetings booked all afternoon.’

Grace stared back at her. ‘Would you prefer us to arrest you on suspicion of conspiracy to murder?’

There was a long, silent stand-off. Then she said compliantly, ‘Would 9 a.m. work?’

Grace glanced at Polly, who nodded. ‘OK, 9 a.m. If you go to reception at the front entrance of the Police HQ in Lewes, they’ll have a car park space reserved for you.’

‘You don’t seriously think I have anything to do with Niall’s wife’s disappearance, do you?’

‘So long as you don’t, Mrs Watkins,’ Grace said, ‘then you have nothing to worry about.’

‘Good,’ she said. ‘Then I’m afraid I have to be off, I don’t want to be late for my class.’