But the vehicle that had pulled up just past the tram stop was not a taxi.

Sharp was waiting outside the entrance to the block when Umber emerged a couple of minutes later, bags in hand, and caught at once his wary glance towards the blue and white camper van.

'Something wrong?'

'Is this our transport?'

Sharp nodded. 'A 1977 Volkswagen T2 in tip-top running order. I bought her second-hand when I retired and did her up proud. Lovely, isn't she?'

'You drove to Prague?'

'I did. And we're driving back. I've booked us on the midnight ferry from Dunkirk to Dover.'

'I thought we'd be flying.'

'Wait till we hit the autobahn.' Sharp winked. 'It'll feel as if we are.'

'Tell me, George,' said Umber, once they were clear of the city and heading west on the main road towards the German border, 'what exactly are we going to do when we get to England?' The van, which Sharp quite unselfconsciously addressed as Molly, had yet to show her alleged turn of speed, but Umber's thoughts were already directed to journey's end. It was one thing to talk about going after the truth, quite another to devise a way of doing so.

'You mean do I have a plan?' growled Sharp.

'Well, do you?'

'Oh yes. But that can wait. First I'd like a little background on you and the last twenty-three years.'

'I'm not going to talk to you about me and Sally, if that's what you're getting at.'

'Force yourself. We need to know as much as each other in case there are gaps to fill in. I'm an open book. Policing in Wiltshire. Then retirement to Derbyshire. No family. No friends to speak of. What you see is what you get.'

'Same here.'

'Oh, I doubt that. I'll hazard a guess about you and Sally and you can tell me whether I'm wide of the mark. The relationship began straight after the inquest.'

Umber was glad Sharp had to concentrate on driving. Otherwise he would have been sure to notice Umber's wince of dismay. The inquest was where it had begun for them. Devizes Magistrates' Court, October 1981. The coroner's summing-up had loaded an unfair amount of blame on Sally's shoulders. She had looked so young and alone, so helpless in the face of criticism. The Hall family had made no move towards her. The press had been lying in wait outside. On impulse, Umber had said to her, 'Come out the back way with me. We'll drive somewhere.' She had looked at him, her eyes full of gratitude. And she had simply nodded her acceptance. It was all she had been able to do.

'The coroner was out of line,' said Sharp. 'I was going to tell Sally that, you know. But you whisked her away before I had the chance. Where did you go?'

'The Kennet and Avon Canal. We walked along the towpath.'

'Nice choice. And what about the decision to go abroad? Christmas, maybe? New Year?'

'You're not going to give up, are you?'

'Not for the next few hundred miles or so.'

'All right. I'll tell you.' Umber knew then that he would have to give Sharp some sort of account of his life with Sally. Better, he decided, an edited one of his own shaping than whatever result Sharp's guessing game produced. 'Sally needed to get away. So did I. She rapidly became more important to me than a Ph.D of questionable relevance to anything. She'd abandoned a teaching degree before working as a nanny, so teaching English abroad seemed the obvious answer for both of us. We took the qualifying course in Barcelona in the spring and summer of 'eighty-two. We worked in Lisbon after that, then Athens, then… all over. The further from home the better.'

'Good idea, I imagine.'

'It seemed to be. We had a few happy years.'

'Only a few?'

'We were in Turkey – Izmir – when we heard about Radd. Sally was pregnant at the time. Miscarried shortly afterwards. I blamed her Turkish doctor. She blamed…' Umber chuckled bitterly. 'Herself.'

'Come again?'

'She got it into her head that she wasn't allowed to have a child of her own… because she'd lost Tamsin.'

'That's -'

'Crazy? Yes, George, you're so right. Crazy is what it was. And it went on that way. I tried to keep her on an even keel. Maybe I didn't try hard enough. Or maybe I tried too hard. Maybe we both did. We got married. But that didn't help. In fact, it only made it worse. In the end, we felt tied to each other. Trapped. We were in Italy at the time. I accepted a job back in Turkey, knowing she wouldn't go with me because of what had happened there. She stayed on in Bologna. She hadn't actually been working in quite a while. Then she went back to England.'

'When was that?'

'Autumn of 'ninety-eight.'

'You were together a long time.'

'Nearly seventeen years. She lasted less than a year on her own.'

They must have covered a mile or more in silence before Sharp said, 'Maybe the coroner was right and it was just an accident.'

'Maybe.'

'But who trails a fan heater on an extension lead into a bathroom on a summer's evening?'

'Exactly. Who does?'

'Blame yourself, do you?'

'What do you think?'

'I think it's handy in this case' – Sharp cast Umber a sidelong smile – 'that you've got someone to share the blame with.'

Blame had hung heavy in the air at Sally's funeral. Umber could remember the almost physical weight of it, pressing down on his shoulders. He had been tempted to plead pressure of work and stay away, but that would have been one desertion too many. So he had gone. And seen the accusations hovering in the eyes of the other mourners. And known that he could not rebut them. He should have saved her. He should have been capable of it. But in the end all he had managed to do was to save himself.

'When love fails, self-preservation takes over,' Alice Myers, Sally's oldest friend, had said to him afterwards. She had not troubled to explain her remark. She had not needed to.

Umber had returned to Turkey the following morning. In simple terms, he had fled. He had been home since, of course. But only now, on this long drive across half of Europe, did he feel that his flight might at last be over.

It was after dark, in a service area near Aachen, over coffee and baguettes, that Sharp unveiled his plan.

'There's nothing very sophisticated about it. Checking facts and asking questions is what it amounts to. I want to know two things. One, who sent me the letter? Two, what really happened at Avebury on the twenty-seventh of July, 1981? Maybe that's basically the same question. We'll see. The great thing is to look on the passage of time as a blessing, not a curse.'

'How can it be?'

'Because it means we can forget all that forensic crap. I never really trusted the white-coated brigade anyway. Fingerprints. Bloodstains. Fibre samples. They don't come into it. But time? That's a different matter. It reveals a pattern. What the people touched by the abduction of Tamsin Hall and the murder of Miranda Hall have done in the years since is the evidence we're going to sift.'

'And what have they done?'

'Well, you and Sally – sadly – we know about. That brings us to the Hall family. How much do you know about them?'

'We heard the Halls had split up.'

Sharp nodded. 'It's not uncommon in cases like this. The death of a child. The loss of another. The parents cling together at first, then drift apart. Their lives are shattered. In the end, it becomes easier to rebuild them separately. The Halls divorced while I was still in Wiltshire. Jane Hall married a local wine merchant. Name of Questred. He used to keep a shop in Marlborough. With any luck, he still does. They had a child of their own, you know.'