‘I’m not sure.’ She closed her eyes and clicked off her light. ‘Everyone, turn your flashlights out.’

‘Why should—’ Vorster began.

‘Just do it,’ she snapped. The others switched off their torches. Nina waited a few seconds, then opened her eyes again.

The eerie sapphire light from above silhouetted Imka and Vorster on the stairs. But she could see her surroundings quite distinctly, lit by a low but clear white glow.

‘That wasn’t there before,’ said Eddie. ‘Where’s it coming from?’

‘I don’t know.’ The source was elusive yet ubiquitous, emanating from all around them. ‘It’s behind the walls . . .’

‘It’s not behind the walls,’ said her husband with alarm. ‘It is the bloody walls! The whole place is glowing!’

‘What?’ gasped Imka. ‘How is that possible?’

‘I don’t know,’ Eddie growled. ‘But the last time we saw a crystal glowing like that, it blew up like a fucking H-bomb twenty-four hours later. Time to leave.’

‘We don’t know that it’s anything like the Atlantean spearheads,’ Nina protested.

‘And we don’t know that it isn’t. We’ve seen weapons, we’ve seen armour – this place is a military installation. Come on!’ He guided her upwards. ‘For all we know, we’ve just set off a booby trap!’

‘Captain, come in. Captain Tate? Torrox, can you hear me?’

Naider stood outside the fortress, the walkie-talkie raised to his ear to catch any reply through the radio interference. None came. His concern grew. Tate was a professional seaman and would never leave the bridge unmanned, especially with a shore party in a potentially risky situation.

Worried, he turned back to the hatch. He had to let the others know he’d lost contact—

A sound reached him over the ice’s constant moans and creaks. An outboard motor, getting closer. Thank God! He went to the end of the ledge and looked towards the cave mouth. A boat came through it.

His relief only lasted moments, replaced by confusion. The Torrox’s only other craft was its lifeboat, bright orange with a fibreglass hull, but this was another rigid inflatable. And there was a second behind it. The new arrivals, four in each boat, weren’t his shipmates. So who were they?

A man in the lead RIB pointed something up at him. He stared at it, refusing to believe what his eyes were telling him. It couldn’t be a gun—

It was.

A flash of fire – and Naider fell back against the icy wall as a bullet smashed through his right shoulder. He staggered . . . and slipped off the ledge.

He tumbled down the cliff, screaming – then his cry was abruptly silenced as he was impaled on the needle-sharp spikes of ice below.

The two boats pulled up beside the Torrox’s RIB. Their occupants jumped out and started to follow the explorers’ path.