‘You mean illegally squatting in the empty apartment block?’ asked Tilsner.

Again, Lotti looked at Müller’s deputy as though he’d lost his mind. ‘No, of course not. Because of what happened earlier. The argument with one of your lot at the building site nearby.’

Things were starting to become clearer in Müller’s head, but the elliptical way Lotti was giving her answers wasn’t helping. ‘The man who died? You’re saying he was a People’s Police officer?’

‘People’s Police. Ministry for State Security.’ The woman shrugged. ‘Same difference, isn’t it?’

‘Not necessarily,’ said Müller. ‘Anyway, in your own words, tell us what happened.’

If Lotti Rolf suspected the police knew less than she thought they knew, she didn’t seem to be showing any inclination to withhold the facts. In fact, she seemed all too ready to tell Müller and Tilsner everything – which itself left a nagging doubt at the back of Müller’s brain.

‘This policeman, or Stasi officer, asked me to arrange a meeting for him with Arnie.’

‘This was after Dr Southwick’s research at the university was supposed to have come to an end?’ asked Tilsner.

‘Yes. Of course.’

‘Why did they ask you to get involved?’ prompted Müller.

‘They must have known we were close. That I had some influence over Arnie. And also, that I knew where he was.’

‘And where was he?’ asked Tilsner.

‘He was hiding out in another half-built building in Gorbitz. Near the one you found us in at Amelie-Dietrich-Platz.’

‘Why the hell did you go back there again?’ asked Tilsner. It was something Müller couldn’t understand either, although it wasn’t the most pressing question that needed to be asked.

‘It was Arnie’s idea. Something about hiding in plain sight. But we moved between there and the culvert in the water meadows every few days to try to keep safe.’ She eyeballed Tilsner. ‘You know. The one you found.’ Then the woman gasped, and held her hand over her mouth. As though she’d said something she hadn’t wanted to. Possibly because one of them had been responsible for assaulting Müller’s deputy when he stumbled across their riverside lair.

‘Tell us more about this meeting with the police or Stasi officer,’ said Müller, trying to draw the interrogation back to the key part. ‘What went wrong?’

‘Arnold lost his temper. Said he’d been tricked. That his life’s work had been ruined.’

‘He lost his temper with this official?’ asked Müller. Then she stared hard at the woman. ‘Or with you for luring him to the meeting?’ Müller remembered Petra Abt’s testimony – the punky art student. She hadn’t mentioned a second man being involved – the argument had been between a man and a woman – presumably Rolf and Southwick. She saw a look of guilt pass momentarily over Lotti’s disfigured face.