‘No, but he sometimes becomes very frightened. Please wait.’ An exchange with the orderly, then she went into the room. Nina remained outside, feeling the weight of the key in her bag.

A minute passed, then there was a gentle rap on the door. The orderly checked through a peephole and opened it. ‘Professor Wilde, come in,’ said Kuiper.

Nina took a pensive breath, then entered.

The room was small but light, a tall, thin window reinforced with fine wire mesh overlooking a leafy quadrangle. A small table was home to a pad of paper and felt-tip pens, but there was no indication they had been used.

It was easy to see why at the sight of the room’s occupant. Wim Stapper was in his late twenties, but any youthful energy had been drained by his ordeal; his face was drawn, a body that had once been strong and wiry now merely thin. He did not react to the new arrival, gazing blankly from the bed at something beyond the ceiling.

The doctor spoke to him in gentle Dutch, but got no response. ‘This is his normal state,’ she whispered to Nina. ‘A near-catatonia. He is aware of us but does not want to respond.’

‘Why not?’

‘Most probably fear. He suffered a traumatic experience before his rescue. The only way his mind can deal with it is by hiding from the world.’

Nina regarded him sadly, feeling a pre-emptive guilt. Something terrible had happened to the young Dutchman, but the only way to find out what would be to remind him of it. ‘Does he speak English?’

‘Yes. Fluently, according to his family.’

‘Can I talk to him?’

Kuiper reluctantly nodded, then checked her watch. ‘Five minutes.’

Nina stepped closer. ‘Hello,’ she said softly. ‘My name’s Nina. I’m an archaeologist – I look for lost things from the past. Things that have been buried.’ She put a little emphasis on the last word. Stapper’s eyes flicked towards her, but then looked back at the ceiling. ‘I’ve found something – something stolen from you when you were rescued from the ice.’

No reaction for a moment . . . then almost inaudible words slipped from his lips. ‘The ice?’

Nina looked at Kuiper, who was surprised. ‘He does not usually react to strangers. But please be careful what you say next. The memory can upset him.’

‘I’ll try my best,’ said Nina, not sure how to dance around the subject. ‘Wim, I’ve got something I’d like to show you. Is that okay?’

This time, he didn’t respond. She gave Kuiper another glance, then slowly took out the golden disc. ‘I have the key.’

‘The . . . key?’ murmured Stapper. He turned his head towards her – and his eyes went wide as he saw what she was holding. ‘The key! No, no! The demons – they want it! They want to kill us all!’