The group attached the container to the ropes Harhund and Martel had secured and rigged the ascender, reversing its motor to lower it to the waiting RIB. It only took a couple of minutes to reach water level. The hard part was now getting it into the boat without swamping or capsizing it, but the heavy coffin eventually came to rest.

Wintz moved off. The RIB was clearly overladen, the mercenary pulsing the outboard with great care to back away from the cliff before slowly turning towards the cave mouth.

Harhund faced his companions. ‘Now we go.’

Nina stood fast. ‘What about the others? I’m not going anywhere until they’re safe.’

The Scandinavian regarded her coldly, then called to a man near the hatch. ‘August, tell Braun to kill Chase.’ The man started back into the fortress. Imka made a sound of horror.

‘No, wait, wait!’ Nina cried. ‘I’ll come with you!’

August paused. Harhund kept his gaze fixed on the redhead for a long moment, then signalled for him to return. ‘Do not push me, Professor Wilde,’ he said. ‘Now move.’ He descended to the lower ledge and started across the cliff.

Martel set off after him, gesturing for Nina to follow. She hesitated – the ropes were already straining against the carabiners under their combined weight – but Roche pushed her. A furious glare at him, then she clipped herself to the line and stepped onto the crack.

The movements of the two men ahead made the rope judder in her grip. She sidestepped after them, keeping her body as close to the ice as she could. She would shed no tears if Harhund fell to his death, but she had no intention of joining him.

Roche obviously had similar thoughts, letting her open up a gap before following. Even so, the addition of a fourth person only added to the stress on the screws. Nina paused as she reached one, hearing faint crackles from the ice around it. Unnerved, she continued. Harhund passed the debris field where Cheng had almost fallen and headed for the outcropping, Martel not far behind.

The mercenary leader glanced back. ‘Roche, keep up!’ he shouted.

Roche made an annoyed sound, but increased his pace. The pouch on his chest meant he couldn’t press himself against the wall, making his movements awkward. ‘Go on, keep moving,’ he told Nina as he closed the gap.

‘We’re too close together,’ she shot back. ‘If one of these screws breaks loose, we’ll all—’

An impossibly deep whump of straining ice – and the whole wall shifted beneath her.

Nina gasped and flattened herself against the cliff. This was no mere tremor; her inner ear told her she was pitching forward. A hissing crash from below. The water churned and frothed, waves smashing against the foot of the glassy wall.

The whole iceberg was moving!