The tale Pirie told him featured a child’s diary written by Karen at the time of Mary’s disappearance. It continued with the trauma of a woman who had apparently foreseen the discovery of her pal’s body, only for that to come true. Then the recovery women’s attempts to help Karen Marshall remember more about the day on which her pal had disappeared, only for Karen to run from them, taking the diary with her.

‘You’ve seen this diary?’ McNab finally interrupted.

‘No, but Marge has, although she hasn’t seen its contents. Karen asked Marge to look after the diary for her, as its presence in the house was haunting her. Then she changed her mind and took it back.’

‘So no one has read it?’

‘Correct. Although Karen says what she wrote down back then isn’t the whole story. There are days she left empty. Days when something happened that she can’t remember. That’s why she was getting the women to ask her questions, to help her try.’

‘So why did she run away from the meeting?’ McNab was trying to absorb what was beginning to sound like a visit to a therapist.

‘You know how McLaughlin told you that Mary was pregnant when she disappeared?’ Pirie was saying.

‘That wasn’t identified at the PM,’ McNab reminded him.

At this point Pirie began to tell a story about white dresses and virginity and whether God would forgive Mary. With every word spoken, McNab felt his distaste rise.

Pirie was watching him, waiting for a response.

‘You’re saying there’s a likelihood that Mary McIntyre was being sexually abused when she went missing?’

‘Marge thinks Karen believes that.’

McNab contemplated all of this, then got back on firm ground. ‘Tell me about the possible crime scene.’

Pirie began to describe his arrival at the cottage, how he’d found the back door unlocked and had entered via the scullery.

‘The light wasn’t on in there, so we didn’t spot the blood at that point.’

He talked about the kitchen. The mobile phone, which they’d heard ring from outside. The chair dressed in Karen’s husband’s clothes.

McNab interrupted him there. ‘How long ago did he die?’

‘Sometime within the last year, I believe. Dementia. Karen never went out of the house towards the end.’

McNab stopped Pirie again when he reached the bedroom scene. ‘She’d created models of her dead husband on the chair and in the bed?’

‘The clothes were laid out on the chair as though he was wearing them. The dummy in the bed was a pair of stuffed pyjamas . . .’

McNab cut him off there, mainly because the last image he’d conjured up was just too powerful. Plus he was already wondering, when or if they found Karen Marshall, whether she could be regarded as a reliable witness.

‘What about the blood splattering?’

‘Only in the scullery. I wondered if she might have cut herself with the kitchen knife that lay in the sink. When the police arrived they checked for a 999 call, in case she’d been taken to A&E, but no. Plus her car’s still there.’