McNab considered this for a moment. He didn’t want to give McCreadie more power in this case than he already had. Still . . .

‘I can spare half an hour,’ he offered.

‘Good,’ McCreadie said briskly. ‘Come over. I’ll get Lucy to put the coffee on.’

As McNab headed there, he had a simple yet profound thought, which seemed to make ever more sense the nearer he got to McCreadie’s house.

What if the former DI, now crime writer, had known all along that Karen Marshall lived just along the road from him?

He was obviously being watched for, as the door of the big stone villa was opened before McNab could even ring for attention.

Lucy greeted him with a smile, fashioned as though for an old friend. ‘Good morning, Detective Sergeant.’

‘Good morning, Lucy,’ McNab reciprocated.

‘Mr Smart is in the conservatory. Coffee, strong?’

McNab nodded his agreement. He might not be fond of McCreadie, but he was definitely partial to his coffee.

McCreadie greeted him with the same enthusiasm as his housekeeper, which immediately put McNab on guard. He wasn’t at all happy with McCreadie playing a part in the investigation, despite the usefulness of the information he deigned to give them.

‘Have a seat, Detective Sergeant. Coffee should be here shortly.’

McNab took a seat, but said nothing, although he was keen to know how McCreadie had been aware that he was in Stirling.

As though reading his mind, McCreadie said, ‘I know about Karen Johnston’s disappearance. News travels fast in Stirling, and we don’t live that far from one another. Plus—’ He halted there as Lucy came in with the tray.

Once she had departed, McCreadie supplied the end of his sentence.

‘As I was about to say, I know Karen.’

McNab almost spilt his coffee at this point.

‘You knew Karen Marshall was here in Stirling and you didn’t inform us?’

McCreadie looked pained by the accusation. ‘I know Karen Johnston, or more correctly, I knew Jack Johnston. He and I used to meet on occasion when he walked their dog on King’s Knot. I don’t have a dog, but Lucy does, and I sometimes take Benji out with me. Walking is good for plotting. It frees the mind.’

He checked on McNab before continuing. ‘Of course, when Jack got ill, he stopped going on walks. I never saw him again. Then I spotted Karen a few days ago. She was walking alone through King’s Knot. Charlie, their black lab, had died, or so I’d heard. I had Benji with me and of course he went up to her with his ball. She looked a bit uncomfortable about it, but she threw the ball, although she definitely didn’t want to speak to me.’

‘Did you recognize her?’

‘As Karen Marshall? Definitely not.’

‘Did she know you?’

‘I’d only met Jack in person, so no to my current persona. If you’re referring to the last time we met officially, that was forty-five years ago, when she was an eleven-year-old traumatized kid and I was a young detective inspector, so I suspect not.’