The cave’s roof was about twelve feet high. Eddie crouched to grab Nina around her lower legs with one arm and support her with the other, then hoisted her upwards. ‘Bloody hell,’ he complained, ‘I used to be able to lift a full-sized bloke and all his gear with no trouble. Getting old is a load of arse.’

‘But think of how much you save on haircuts!’ she replied, rubbing his bald head before looking up. At full stretch she could reach the crack, but first she needed to see what was inside it. She fumbled out her phone and switched on its light.

A dark purple stone was revealed. Set into it was a crystal splinter . . .

‘I think I’ve found how they got in,’ she said with excitement – and trepidation. She extended a finger, brushing its tip against the inset stone—

A crack of energy made her jerk away. ‘Whoa, shit!’ she gasped, arms whirling as she overbalanced. Eddie dropped, rolling backwards to catch her. She landed on top of him with an undignified squawk.

Macy ran to them. ‘Mom! Dad! Are you okay?’

Nina struggled off her husband. ‘Yeah, I think so. Eddie?’

He half grinned, half grimaced. ‘I’m okay. Who needs ribs anyway?’ He sat up. ‘So, did it do anyth—’

A deep, grinding thud echoed through the cave.

The two rangers drew back in alarm. ‘What was that?’ said Barney.

‘I think,’ Nina replied, helping Eddie to his feet, ‘it’s a secret entrance.’

Dust and sandstone flakes spat from the rear wall – and the vertical crack widened as the whole section of rock slowly swung back to expose a dark passage. ‘Wow!’ Macy gasped.

She was about to take a closer look, but Eddie stopped her. ‘Let’s make sure it’s safe,’ he said, turning to the rangers. ‘I need that gun.’

Sandra shook her head. ‘I can’t let a civilian have it.’

‘I’m ex-SAS, I know what I’m doing. And I know what we’re facing – you don’t. If one of the ten-foot-tall bastards who killed your friend comes charging out of that tunnel, you might hesitate. I won’t.’

She unhappily handed the weapon to him, and he checked it over. It was a basic wooden-stocked Beretta bolt-action hunting rifle, its magazine holding six .223-calibre rounds. Deadly enough – if the first shot was on target. If the iron sights were off, the moment needed to cycle the bolt and reload could be enough to bring retaliatory fire upon him. ‘Right, everyone back up.’ He waited for the others to retreat into daylight before going to the opening, aiming the rifle inside.

The tall passage sloped down into Uluru’s heart. It looked like a natural cleft that had been widened by hand. No movement in the shadows. Gun raised, he cautiously moved deeper and took out his own phone. Its light revealed only red rock as the tunnel snaked into darkness.