Somewhere in all this material – the statements, the forensic evidence, the interviews, the diary, his talk with Karen – was the truth. Concocted stories were never airtight and this was a concocted story. A web of remembrance, the criss-crossing of multicoloured threads, some strong, others weak.

The past is what we decide it to be.

No one in this was telling the truth. All of them were telling their own truths. The ways in which they wanted to remember it. The ways in which they could cope with that memory.

Karen had buried her story in order to survive it.

McNab chose the one thing he believed didn’t happen, then questioned himself whether it had. What had so traumatized Karen that day that she had ceased to speak at all? What had she buried so deep in her subconscious that it had remained hidden there for forty-five years?

Karen had told him she’d always hoped that Mary had run away, and would eventually come back. Maybe that was the lie she told herself in order to survive, because she knew it wasn’t true.

Karen, McNab realized with certainty, had always known her friend was dead.

She had known because Karen had seen Mary killed. Or she knew because Karen had killed her. The shocking and possible truth of each of these scenarios began to play out in McNab’s head.

Firstly, the one he definitely didn’t want to be true. The girls fighting over who would wear the dress. In the struggle, Mary falls badly, hits her head. Karen can’t rouse her. Would she do as she said and go to the chapel in Mary’s place? Or just run?

The scenario, although possible, required an adult to remove the body and bury it. Would Karen tell anyone about the accident, and if so, who?

It came to him then that if she told anyone, it would be her policeman father. And what would he do? Report his daughter? See her locked up for all her young life? Or remove the evidence? All the evidence that the girls had ever been at the den that day.

The impossible had just become the probable.

But what about the marks on the body that suggested a sexual motive for Mary’s death?

DC Kenny Marshall would have known what to do, in case the body was ever discovered. McNab suddenly recalled the gentle way in which the body had been laid to rest, the pillowed head resting on the confirmation dress. Would a sex-crazed killer have done that?

McNab realized he was the one writing the story now. Fashioning it in his own way to fit the known facts.

And yet . . . what was it Karen had said at the completion of their talk?

My dad told me I had to forget everything that happened that day. I was just a wee girl. I didn’t understand what was going on. Except, she’d added, if Mary was dead, it was my fault.

McNab had chosen to use the car to visit Eleanor Jackson, rather than the bike. The Harley would have got him there faster, but he couldn’t think so well when riding it, his exhilaration taking up all of his thoughts.