‘Thank you for making the time to see me,’ Tony said, shaking her tiny plump hand.

‘It’s my pleasure. It’s always interesting to have a break from routine. So, why don’t we have a coffee and you can tell me exactly what it is that interests you.’

He followed her through a small studded wooden door at the base of the keep and down a flight of worn stone steps. ‘Mind your step,’ she cautioned him. ‘These stairs can be treacherous. Best to keep close to the handrail.’

They turned into a low corridor, lit with glaring fluorescent strips. ‘We have the least attractive quarters in the castle,’ Dr Wertheimer said. ‘The part the tourists never get to see.’ She turned abruptly into a doorway that opened into a large room lined with utilitarian metal shelving. To his surprise, it had narrow lancet windows along one wall. ‘Not a very enticing view,’ she said, noting his glance. ‘We look out on to the ditch. Still, at least I have some natural light, which is more than most of my colleagues. Please, take a seat, make yourself comfortable.’

Tony sat in one of a pair of battered armchairs set in a corner of the office while Dr Wertheimer fussed with kettle and coffee pot. She brought him a mug of startlingly viscous coffee and settled herself in the chair opposite him. ‘I’m very curious,’ she said. ‘When I spoke to your colleague from Berlin, she was reluctant to give me any details of the nature of your inquiries.’

Tony sipped cautiously. There was enough caffeine in the brew to keep a narcolept awake for days. ‘It’s a very sensitive matter,’ he said.

‘We’re accustomed to sensitive matters here,’ Dr Wertheimer said tartly. ‘Our archive contains material that is still extremely uncomfortable for my fellow countrymen to contemplate. So, I need to be clear about the purpose of your visit. You can speak confidentially to me, Dr Hill. It won’t go any further.’

He sized up the placid face with its sharp eyes. He was inclined to trust this woman, and he suspected that, unless he opened up to her, she would be reluctant to do the same for him. ‘I’m an offender profiler,’ he said. ‘I was brought in to help with an investigation into a series of murders that we believe have been committed by the same person.’

Dr Wertheimer frowned. ‘The university lecturers?’ she said sharply. Astonished, Tony simply gaped at her. ‘You have not seen the newspapers this morning?’ She got up and rummaged in a large shopping bag at the side of her desk. She produced a copy of that morning’s Die Welt and turned to an inside page. ‘You read German?’ she asked.