The hire car was waiting for Tony at Frankfurt, just as Petra had promised. He was grateful that she’d found the time to organize his trip; it would have been so much harder if he’d had to make his own arrangements. On the passenger seat was an internet-generated route plan to get him from the airport to Schloss Hochenstein in time for the appointment she’d arranged with the curator of the castle’s grisly records. He didn’t imagine he was going to find the ultimate answer to his quest this morning, but at least he might be able to leave with a list of names that could be used as a cross-reference if Marijke and her German colleagues managed to come up with possible candidates from the shipping community.

Even on a sunny spring morning, Schloss Hochenstein was a grim sight. The winding road that led up from the valley floor to the castle sitting on its bluff offered occasional glimpses of its forbidding grey walls and turrets. This was no fairytale Rhineland castle, he realized, as he rounded the final bend and came face to face with the looming edifice. There was nothing graceful about the schloss. It hunkered on top of the tor like a fat toad, everything about it heavy and overbearing. The towers on each corner were squat and ugly, the crenellated battlements threatening. This was a place to strike fear into the heart of your enemies, Tony thought, gazing up at the facade.

He parked in the visitor car park to one side of the castle and walked across the lowered drawbridge. Instead of a water-filled moat, there was a deep stone-lined ditch with savage iron spikes festooning the sides and bottom. Above the gateway were elaborate stone carvings of mythical beasts engaged in combat. A griffin crouched on the back of a unicorn, its claws buried in the unicorn’s neck. A strange serpent had its fangs plunged into the throat of a wyvern. As symbolic greetings went, Tony thought they might as well have carved, ‘Abandon hope all ye who enter here,’ and have done.

In the gatehouse, there was a ticket office. Tony walked up to it and told the attendant he had an appointment with Dr Marie Wertheimer. The man nodded gloomily and picked up the phone. ‘She will be with you now,’ he said, indicating to Tony that he should proceed into the courtyard of the keep. High walls towered over him, their narrow windows suggesting an army of hostile eyes. He imagined how this must have appeared to the frightened children herded here and shivered in spite of himself.

A rotund figure approached across the courtyard, swathed in a maroon woollen wrap. The woman looked like an autumn berry on legs, her greying hair twisted on top of her head in a neat bun. ‘Dr Hill? I’m Marie Wertheimer, curator of the records here at Schloss Hochenstein. Welcome.’ Her English was almost without accent.