Fry began to move restlessly around the office. She walked to the window and back again towards her desk, as if a change in the direction of the light might help her to see things more clearly.

‘If she did that, she was sealing Lindsay Mullen’s fate,’ she said. ‘It looks as though Rose Shepherd was already being watched when she went into Matlock Bath that day, doesn’t it? And whoever was watching her must also have followed Lindsay home.’

‘Why would Miss Shepherd pick on Lindsay to talk to?’

‘Why pick on anybody? For heaven’s sake, who buttonholes complete strangers in cafés and engages them in conversation?’

‘Drunks and nutters,’ said Murfin.

‘Exactly. And Rose Shepherd was neither of those.’

‘Well, she had to be a bit odd. This woman was a hermit with a secrecy obsession.’

‘That’s right. You don’t have to be a complete nutter,’ said Cooper. ‘Rose Shepherd had cut herself off for so long, perhaps she just wanted a few minutes of ordinary conversation, even with a complete stranger. In fact, a stranger is a better choice. They don’t know anything about you, or your past. So they don’t start off with preconceptions about you.’

‘If she was that desperate, why didn’t she talk to Eric Grice? Whenever he came to Bain House, Miss Shepherd kept herself out of the way and refused to engage in conversation.’

‘Maybe she was afraid that, once she started talking, she wouldn’t be able to stop. She couldn’t risk it.’ Cooper looked up at her. ‘You know what it’s like yourself. When you’ve got something preying on your mind and you find someone easy to talk to, it all comes spilling out.’

‘Really?’

‘Oh, well – maybe not you, Diane.’

‘Thanks,’ she said, and meant it.

‘But take it from me, it works that way with a lot of people. You can find yourself telling everything to some sympathetic stranger who’s prepared to listen. I think Rose Shepherd was so scared of giving away clues about herself that talking to people was too much of a risk. So she avoided it. Simple as that. A bit like a recovered alcoholic avoids taking the first drink. It’s not the one drink that’s the problem – it’s what he knows it will lead to.’

Fry began to pace the room again. ‘OK. So what was she hiding?’

‘Well, that,’ said Cooper, ‘I don’t know. I can’t imagine what it’s like to be so alone, to cut yourself off from everyone that way. How could anyone do that?’

‘Why are you asking me?’

Cooper raised an eyebrow at her tone and looked around the room. ‘Apart from Gavin, there’s no one else here, Diane.’

Fry was silent for a while, staring down at the floor. ‘This is getting us nowhere. Instead of all these what ifs, we need to start finding some answers.’

‘Sounds good to me,’ said Murfin. ‘So when do we start?’

‘Gavin –’

‘Sorry.’

‘Well, I know one thing,’ said Cooper. ‘It’s difficult to see a connection between the fire and the shooting. And now Simon Nichols – how does he fit in? I suppose if he didn’t die until Tuesday, he could have been involved in both incidents.’

‘Hold on,’ said Fry. ‘So far as we can tell, there were nearly twenty-four hours between the two. In Rose Shepherd’s case, the medical examiner gave us a pretty wide range for time of death – between thirty and forty hours. But let’s get this straight – the Foxlow shooting came first. It’s just that the victim wasn’t discovered until after the fire.’

‘Maybe Lindsay Mullen was in the wrong place at the wrong time, then. She must somehow have got a look at Nichols, or whoever was watching Rose Shepherd. A good enough look to be able to identify him later.’

‘So he decided to take her out before she could give anyone a description?’

Cooper nodded. ‘Before she even knew that Miss Shepherd had been killed. The body wasn’t discovered until Monday afternoon.’

‘Somebody wasn’t taking any chances, were they?’

‘It’s because they’re –’

‘Yes, I know. Professionals,’ said Fry. ‘That’s another factor against Nichols. If he wasn’t a professional himself, he had the right contacts.’

‘Well, we’ll have to wait for the PM results before we know more about Nichols.’

Fry stared at the ceiling for a few moments. ‘You know, you were right – the Shepherd enquiry is becoming a big distraction for me. I should be focusing on the arson.’

‘What do you mean?’ said Cooper.

‘Well, there are easier ways to kill somebody, don’t you think? Easier than breaking into their house and setting fire to their sitting room. More guaranteed to get the right results, too – because, if the smoke alarm had been working properly, the Mullens might have escaped.’

‘Perhaps not that much easier, if you want to make it look like an accident.’

‘An accident?’ Fry tapped the Rose Shepherd file. ‘That doesn’t sound like the Foxlow suspect, does it? There was certainly no attempt to make Miss Shepherd’s death look like an accident. Quite the opposite – it was done openly and audaciously, like some kind of warning: “Look, we can get to anyone, anywhere.”’

‘Ye-es,’ said Cooper.

Fry looked at him sharply. ‘I take it you’ve formed a different opinion, Ben?’

‘Well, just because there was that difference it doesn’t necessarily follow that they weren’t connected, does it? Our suspects might have had some reason for wanting to make the fire look accidental, but not the shooting of Rose Shepherd.’

‘What reason?’

Cooper shook his head. ‘I don’t know …’

‘No. But what we do know at the moment is that Rose Shepherd had connections with a Bulgarian criminal, who’s also been found dead. We don’t have any more information on Nikolov until we get PM results and the intelligence files from Sofia.’

‘You almost make that sound like a good thing, Diane.’

‘Well, it means I can focus on the Darwin Street fire for a while. Unrelated, or not.’

A few minutes later, Fry finished reading the postmortem reports on the Mullen family for the second time. She put the report aside, then recalled what Mrs van Doon had said about the victims being confused and disorientated by the inhalation of smoke.

She picked up the phone and rang Scientific Support. Wayne Abbott, one of her favourite people.

‘Wayne, you know you said the fingerprints in the house at Darwin Street all belonged to members of the family?’

‘Yes?’

‘Which members of the family did you mean specifically?’

‘Hold on …’ She heard the rustling of paper as he found the right file. ‘Here we go. Well, as you might expect, there were prints from the householders everywhere – that’s Mr Brian Mullen and Mrs Lindsay Mullen. And the children, of course. They were easy to differentiate because of their size.’

‘OK.’

‘Right. Those prints were mostly from the relatively undamaged parts of the house, you understand.’

‘Like the kitchen?’

‘Exactly. I mention that because we lifted a couple of prints belonging to the grandmother, Mrs Moira Lowther. We asked all the family to give their prints for elimination purposes, of course. But hers were only in the kitchen. Nice, smooth surfaces for us to dust, you see. We found none from her husband, though. That doesn’t necessarily mean anything. There was so much damage in the sitting room –’

‘Anyone else on the list?’

‘Yes, the dead woman’s brother, Mr John Lowther.’

‘Where were his prints?’

‘Oh, kitchen, bathroom, sitting room. Some of his were on the children’s toys that we salvaged. I expect he used to spend some time playing uncle with the kids, don’t you think?’

‘Yes,’ said Fry. ‘That’s probably it.’

The engaged sign was showing on the door of Interview One. Inside, John Lowther seemed to be sweating. Damp patches had appeared under his armpits, and his glasses were slipping on his nose. He looked like a man caught performing some shameful act. Yet all he was doing was sitting in a police interview room, waiting for the questions.