Her discomfiture at Cheng’s question meant the end of class soon afterwards came as a relief. ‘So, Professor Wilde,’ said Aiden, ‘what’re your other rules of archaeology?’

‘There’s only one more,’ Nina replied, with a half-smile, ‘and it’s simple: try not to blow everything up.’

‘You need a rule for that?’ asked Madison.

‘You’d be surprised.’

She gathered her belongings, noticing Cheng leaving in a hurry. She couldn’t dispel her suspicion that he knew about her encounter with the religious organisation known as the Covenant of Genesis. But how could that be possible? She had – with great reluctance – agreed to keep her knowledge of the ancient race known as the Veteres a secret for exactly the reasons she had given. Not that it ultimately had mattered. All evidence of their existence had been destroyed, and every member of the Covenant itself was dead.

Coincidence, she decided as she headed out. There were already numerous theories about ancient precursor races on the kookier fringes of the archaeological world; Cheng had just come up with his own take. Nothing to be concerned about.

That thought lasted for as long as it took her to reach her office – outside which Cheng was waiting. ‘Can I help you, Mr Hui?’

‘Actually, yes, Professor,’ the young man replied, almost twitching with eagerness. He glanced up and down the corridor. ‘But in private?’

She decided to humour him. ‘Come on in.’

Her office on the ninth floor of Columbia University’s Schermerhorn Extension overlooked Amsterdam Avenue, traffic noise rising from the street below. A lifelong New Yorker, Nina had long ago tuned it out. She sat at her desk and gestured to a chair. ‘So what have you got?’

‘I didn’t want to say anything in front of the others,’ he said, sitting. ‘Partly because I didn’t want everyone to make fun of me, but also because if it’s real, it could be an even bigger discovery than Atlantis. I think I’ve found what I was talking about in class. Evidence of a civilisation that existed before humans!’

She gave him a deliberately non-committal nod. ‘I’m listening.’

He opened his laptop, a new, sleek and, she guessed, very expensive model. ‘Okay, there are places on the dark web where people buy and sell stolen antiquities.’

‘I know.’ Certain corners of the internet were home to all manner of criminal activity, relying upon encryption, anonymity and obscurity to hide from law enforcement. Unlike the mainstream internet, it was impossible to find such sites using a search engine; access was by invitation only, buyers and sellers of looted items using near-untraceable cryptocurrencies to cover their financial tracks. ‘It’s a real problem.’

‘I managed to get into one of the sites – I pretended to make friends with someone involved and bought a password,’ Cheng explained. ‘I was looking for stolen Chinese artefacts so I could tell the authorities. But instead . . . I found this.’