‘The morning will be fine,’ McNab said, obviously keen to get off the phone and back to his evening’s entertainment.

As Magnus got out of the car, Marge suddenly appeared back.

‘She’s not answering the door. I’ve knocked and called for her. Something’s wrong, I can feel it.’

Magnus followed her back and added his attempt at getting an answer. When that didn’t work, he said, ‘Try her mobile again. See if we can hear it ring.’

Marge did as requested and they both listened. At first all they could hear was the distant rumble of traffic from the main road, then Magnus did hear something.

‘That’s it,’ Marge agreed. ‘That’s her mobile. God, why isn’t she answering?’

Lots of possibilities flitted through Magnus’s mind, most involving suicide, but he didn’t voice them.

Instead, he headed for the lit window but found the curtains drawn. ‘I’ll check at the back,’ he told Marge. Using his phone torch, he picked his way along a gravel path and round to the back door. A small scullery window shared light from what he now assumed was the kitchen.

He tried the back door, expecting it to be locked like the front. It wasn’t. He shouted to Marge. When her own phone torch turned the corner, he could make out her face, which now appeared more determined than frightened.

‘This door isn’t locked,’ he told her.

‘I’ll go in first, Professor,’ Marge told him in no uncertain terms. ‘Karen won’t be afraid of me.’

Marge pushed open the door.

‘Karen,’ she called. ‘It’s me, Marge. I just wanted to check you’re okay. The girls are worried about you.’ Her voice, firm and clear, seemed to resonate in the emptiness.

Magnus followed a little behind, conscious that the scene that could meet Marge might be worse than terrible. As he entered the kitchen proper, he saw with relief that it was empty. There were two high-backed easy chairs, one on either side of an oil-fired range. A mug stood on the right-hand corner within reaching distance of whoever had sat there. Beside it sat the mobile.

The other chair housed a jumper spread out against the seat back, the sleeves along the arms. Below, a pair of trousers had been placed as though someone was wearing them, a pair of slippers below.

He turned, hearing a small distressed sound from Marge.

‘She can’t let him go,’ she said.

Magnus pulled himself together. ‘I’ll check the other rooms.’

He entered the hall, with its porch leading to the outside world. Crossing it, he opened the far door and clicked on the light. His immediate impression was of abandonment and cold. The open fireplace, he guessed, hadn’t been used for some considerable time. The room was empty.

What about the bedroom?

Off the hall was another smaller passageway, leading towards the back of the house. Magnus followed it past a bathroom to a final door at the end.

He hesitated. If Karen was in the house, it had to be in here. Gently, he turned the handle and opened the door. From where he stood he could clearly see the bed and the humped shape of a duvet, which, he knew, would have to be checked.