Sadie’s recollection of the actual interview was broken and disjointed. She had done her best to play the part: a girl who had only just discovered that the police were looking for her, a girl who’d been mugged, a girl who flinched and became wide-eyed at the shocking news of the deaths of Mona Farrell and Peter Royston.

There had been a lot of toing and froing, officers entering and leaving the room. She had the sense of phone calls being made behind the scenes, of information being confirmed, details being checked, before the next set of questions was thrown at her. Why had she come to London? Where had she been staying? What had her attackers looked like? Why did she think Mona Kellston had come to Kellston? She had held her nerve. She had kept it simple. She had stuck to her story.

Eventually, she’d been released, but this had only been a reprieve rather than an ending to the affair. Back in Haverlea, she’d had to go through it all again, this time under the cool, judgemental eyes of Inspector Gerald Frayne. He had not believed her; she had seen it in his gaze and in the tight, straight set of his mouth. Over and over he had tried to catch her out, phrasing the same questions in different ways.

‘Why did Mona Farrell call herself Anne?’

‘When we bumped into each other on the train, she told me that she didn’t like the name, that everyone called her Anne now.’

‘Really?’ Frayne said. ‘Only her family claim that no one ever referred to her that way.’

‘It’s what she told me.’ Sadie had given a light shrug. ‘I hadn’t seen her for years so…’

‘You didn’t think it was odd?’

‘Not everyone likes the name they’ve been given.’

It had gradually become clear to Sadie that the inspector had nothing on her. Oh, plenty of suspicions, that was for sure, but nothing he could prove. There were witnesses to her being at the fairground, but no one had seen her with Mona Farrell or Peter Royston. In the end, unable to charge her with anything, Inspector Frayne had let her go.

Although Sadie had finally managed to walk free, she had not escaped unscathed. Sometimes there was damage that could never be undone. The twisted mind of Mona Farrell had left a legacy and nothing could ever be the same again.

She remembered the look in Joel’s eyes, the horror and the pity when he’d seen her again for the first time. But over the next few days, as the initial shock subsided, his concern had been replaced by confusion and an endless barrage of questions: What had she been doing in London? Why hadn’t she told him about Mona Farrell and ‘Anne’? Why hadn’t she called to let him know that she’d been attacked?

‘I was only away for a few days. None of this makes any sense, Sadie.’

And he was right. It didn’t. It was a tissue of lies, but she had no choice. She couldn’t tell him the truth. To do that would have meant asking him to keep secrets, to scheme and deceive, to go against everything that made him who he was.

Joel had known that she was hiding something and the knowledge was a barrier between them, a wall that grew higher by the day. Her silence only made things worse. By refusing to talk, to explain, she fed his suspicions, creating a distrust that ate away at their relationship. As Christmas approached it had become clear to both of them that something had been broken – and could never be fixed.

Sadie finished her packing and took a final look round. Was there anything she’d missed? Her gaze skimmed the room, alighting on the framed photo on the dresser: her and Joel standing in the back garden with their arms round each other. She crossed the room and picked it up, a pain pulling at her heart as she ran her thumb across the glass, a final touch of his face before she left for ever.

Before the tears could start, Sadie put the picture down again. She fastened the suitcase, took it down the stairs and left it by the front door. Then she went back up to the flat, stood by the window and waited for the taxi to arrive.

Only a fraction of Gerald Frayne’s attention was on the Nine O’Clock News – unemployment down, a new Honda factory to be built in Sunderland; most of it was focused on the file balanced on his lap. He glanced up at the TV, sighed and returned his attention to the thick sheaf of papers.

Nina looked over at him. ‘You’ll wear that file out. How many times have you been through it this week? I thought the case was closed.’

‘There’s something we’ve missed. I’m sure of it.’ Frustrated, he flicked back a few pages. ‘It doesn’t add up. I mean why would Mona Farrell kill Eddie Wise? There’s no rhyme or reason to it.’

‘But you said they found her fingerprints in his flat. And wasn’t there a receipt for a knife in her purse?’

‘Oh, I’m not disputing that she actually killed the man, I just can’t figure out why. I mean, Peter Royston I get – he was sniffing round, threatening to expose her – but Eddie? What did she have against him?’

‘Did she need to have anything against him? I thought she had a history of psychiatric illness.’

‘Yes, but nothing like this. And he wasn’t just some random victim. According to Sadie Wise, she and Mona bumped into each other on the train, had a brief chat, a bit of a catch-up and then went their separate ways. That was on the Friday evening. By Sunday afternoon, Eddie Wise was lying dead on the kitchen floor with a knife through his chest.’

Nina took a sip of cocoa while she pondered on this. ‘Maybe, in some kind of twisted way, Mona thought she was doing Sadie a favour. There were problems, weren’t there, over the divorce? Hadn’t Eddie been avoiding the issue for quite a while?’

‘Years, apparently.’

‘Well, there you go.’

‘But how did Mona even know where he lived? London’s a big place. And fine, Sadie might have told her that she was starting the search in Kellston, but at the time – or so she claims – she didn’t even know where he was living herself.’

‘You think she’s lying about that?’

Gerald gave a snort. ‘I think the truth and Sadie Wise parted company a long time ago. None of it adds up. According to Joel, Sadie was trying to avoid Mona Farrell, refusing to take her calls, and yet she still went to meet her at the fair. Then there was all that business at the funeral. And why did she suddenly take off for London as soon as her boyfriend’s back was turned? No, it stinks; it’s rotten to the core.’

‘What’s Ian McCloud’s take on it all?’

Gerald’s old colleague at Cowan Road had kept him in the loop as the London side of the investigation had progressed. ‘His theory is that Mona had some kind of obsession with Sadie. There were press clippings found in a shoebox in her bedroom, pictures of the happy couple on their wedding day, except Eddie had been cut out of them all. And there were other items that had been taken from the Haverlea flat – not valuables, just personal stuff, an empty perfume bottle, a lipstick, strands of fair hair pulled out of a comb.’

Nina inclined her head, gazing at her husband. ‘But if Mona was fixated on her, it’s hardly Sadie’s fault.’

‘Unless she used that obsession to her advantage.’

‘Which was what, exactly? Even if she did somehow manipulate Mona into murdering Eddie, then why turn up at his flat? Why go and talk to him about the divorce? She was putting herself in the frame when she didn’t need to.’

‘Maybe it was too late by then.’ Gerald pressed on his temples with his fingertips, feeling the start of a dull, throbbing headache. ‘She was already in London and people knew she was looking for him. By getting Eddie to sign the papers, it would look like she didn’t have a motive. And maybe… maybe the timing was off. Perhaps Mona made her move earlier than she was supposed to. Another few hours and Sadie Wise would have been completely in the clear.’

‘But if she had his signature, she had her divorce – so why have him killed at all?’