He turned the screen to show her. It was a picture of a metal object: a golden disc. At its centre was a circle of stone and crystal. Nina didn’t recognise it – but she did recognise what was scribed into its surface.

She tried to conceal her alarm. The symbols looked very much like the written language of the Veteres. ‘That’s . . . an interesting piece. What is it?’

‘I don’t know. The seller, who’s in Germany, called it a key, but didn’t say much more. I don’t think he knows much more. I suspect he stole it. But I’ve believed for a long time there was a much earlier civilisation than anything we currently know. I think this is proof.’

She raised an eyebrow. ‘A long time? How old are you, Mr Hui?’

‘Eighteen, Professor.’

‘And you’ve been challenging the archaeological establishment since . . . puberty?’ She immediately felt almost guilty at the jibe. It was the kind of dismissal she had faced early in her own career.

‘I’ve always wanted to be an archaeologist, Professor,’ said Cheng, not quite hiding a frown. ‘Just because I’m young doesn’t mean I haven’t worked hard.’

‘Of course not. My apologies. But if there’s any evidence of a non-human precursor civilisation, I’m not aware of it.’

He gave her a probing look. ‘I’ve studied the mythologies of the Hebrews, the Hindus, my own country. There are many common aspects, even when they describe fantastical things. Shared legends. And you’ve proved many times that legends can be based on reality. Atlantis, Hercules, King Arthur, the angels of the Book of Revelation – you found them all. I think this,’ he indicated the item on the screen, ‘is another one. And it’ll prove my theory, when I obtain it.’

‘Jumping the gun a little, aren’t you?’

‘No, I’ve been in contact with the seller. I’m going to Hamburg to buy it.’

‘What?’ said Nina, alarm returning for a different reason. ‘Ethical considerations aside, that’s insanely dangerous! People selling stolen artefacts on the dark web are by definition criminals. There’s a good chance they’ll take your money and give you nothing, but if you meet them in person they might give you something – a beating! How much does the seller want?’

‘Fifty thousand euros.’ The reply was matter-of-fact.

She was shocked, by both the amount and his insouciance. ‘Fifty thou— And you’re planning to pay it?’

‘My family is rich.’

‘You know what else rich families pay? Ransoms!’

‘He seems trustworthy,’ Cheng insisted.

‘Con men always do, right up until they disappear with your money.’ A grim thought. ‘Please tell me you’re not planning to pay this guy in cash.’ His hesitation was answer enough. ‘You might as well go dressed as a lamb with a sign saying “Hello, wolves”!’