Nina followed him into what turned out to be a large cave. A path had been carved along one sloping side. Below was a dark expanse: a pool of water, stretching the cavern’s length. Its surface shimmered as droplets fell from the ceiling with almost musical plips and plops . . .

Wait – how could she even see the surface?

She looked up – and gasped.

The entire ceiling was alight with a galaxy of tiny blue-green stars. ‘What are they?’ Cheng asked, awed.

‘Glow-worms,’ said Eddie. ‘Saw some once when I went caving – when I was still in the army, long time before I met you,’ he added to Nina. ‘These are a lot more impressive, though.’

‘Never seen anything like this before,’ said Barney, also amazed. ‘There aren’t any glow-worms in this part of the country.’

‘There are now,’ Nina said. ‘It could be a new species. Maybe they’ll name it after you.’

‘Miserablus gittus,’ Eddie whispered to her. She tried not to laugh. ‘Must be cracks in the rock to let water down here – and for bugs to get in so the worms can catch them. But this is a pretty big pool, and it smells fresh. Maybe whoever built the tunnels used it as a reservoir.’

‘It’d make sense,’ said Nina. ‘But as beautiful as this is . . .’ She aimed her light at the water and reluctantly clicked it on. The cavern appeared around her, but the spectacular display above instantly vanished, even a single flashlight overpowering it. ‘We need to keep going.’

Barney turned on his own torch. ‘Over there.’ The path continued to an opening in the far wall.

Nina led the way. They were still on the Nephilim’s trail; there had been no side passages large enough to fit even a human, never mind the giants. Beyond the cave, the tunnel resumed its downward course. She paused, listening for activity below. All she heard was the music of the pool. She resumed her descent towards whatever lay at the heart of Uluru.

A hundred miles to the north, a commercial air freighter powered through the sky at thirty-six thousand feet. Cargo China International flight IV283 was on a regularly scheduled journey from Guangzhou in southern China to Sydney, having stopped at Singapore to unload some of its cargo.

This time, though, the Boeing 777F had a last-minute change of manifest before starting its voyage. This came as an unwelcome shock to its crew, who knew they would be endangering their careers, their freedom – they would be arrested on landing – and the aircraft itself. But their orders had come from the very highest levels of government, and even the biggest Chinese corporations existed entirely at the whim of the Communist Party. Failure to obey, the airline’s senior executives were told, would result in their arrests on any number of charges of crimes against the state before the day was over.