‘Have you had cleaners in here?’ Sarah asked him.

‘Yes. We both work hard enough. I fixed up some springcleaning through someone at the office.’

‘Well they did a good job, whoever they were. Could we get them for Edinburgh?’

Bob laughed a strange laugh. ‘You never know what people’ll turn their hands to when they retire. But I think this was a one-off.’

Sarah was given in marriage by her father. Alex and Andy were brides-maid and best man. Among the guests were Chief Constable and Mrs James Proud, Detective Inspector Brian Mackie, Detective Sergeant Maggie Rose and Mario McGuire, and Detective Constable Neil Mcllhenney.

Not one of them, not even Andy Martin, had ever asked Skinner what had happened on that explosive night — after he and Allingham had driven off in the dark towards Gullane.

Only Sarah knew of the weight that he was carrying. Long after his leg had begun to heal, she felt him toss and turn in the night. Occasionally he would awaken in a lather of sweat, and once or twice with a scream dying on his lips. But she never asked. She waited for the shrapnel buried in his soul to work its own way to the surface.

‘Love, I think you should tell me now. I’m your wife, and if something makes you wake up trembling in the night, I want to know what it is.’

And so he told her. He told her the whole story of the night that he had finally discovered that there was a world where Skinner’s rules of honesty, fairness and mercy did not apply; the night when he had been forced to look into his own character and learn the depth of the ruthless streak that lay within him.

‘Do you know what Maitland said? He told me that I’d be a sensation in his line of work. And d’you know what? The fact that we’re sat here, and he’s buried in an unmarked hole in the ground somewhere, proves just how right he was. What sort of a guy am I, Sarah?

‘That was an awful man, a terrible creature. But he finished the job he was sent out to do. Al-Saddi died, and the Day of Deliverance went with him. There was a clear, warped logic to everything he did. All the victims — he saw them as casualties, necessary to his success. There are two million people alive in Israel who would agree, if they knew the story. But ask Iain Mac Vicar’s mother. What would she say?’

‘And you, Bob. Do you think you’re a casualty too? Is that what’s eating you?’

‘Probably. I got into this job because I believed that I knew the difference between the good guys and the bad guys, and I knew what I was. Now I don’t know that any more, not for sure. All I do know for sure is what I’m capable of.

‘Skinner’s Rules! I broke them along the way, and in the end I broke the biggest commandment of all. I was warned off, but ignored it because I never doubted that what I was doing was right. Then I found that I was in a place where right and wrong were immaterial, and where only results mattered. And the really terrible thing is, I survived there. I took Maitland on, on his own terms, on his own turf, and I won. That makes me just like him, doesn’t it?’

Sarah answered the question in his eyes, as she took his hand and entwined his fingers in hers.

‘Bob, if you had lost, and Maitland had come for me, and we were both in Dirleton Cemetery instead of sitting under that big full moon up there if that was how it had turned out, would Maitland have been sitting somewhere agonising about it?

‘The hell he would!

‘When good faces evil, it doesn’t win through being nice all the time. It wins by being brave, and it wins by being right.

‘And take it from me, Skinner. The good guy won.’