Wait! An opening, half hidden by a buckled orichalcum panel. ‘In here!’ he cried, letting Imka slip through before squeezing into the narrow gap.

But his hope that it would lead to an escape route was instantly dashed. The small room had no other exits. Imka spun to face him, her expression almost accusing. They were trapped!

Nina gripped the rope as the cliff shuddered. Somehow, the fortress was trying to break free—

An explosive crack echoed around the cavern. She turned her head – and saw a truck-sized spearhead of ice plunge from beside the Dionysius to strike the water like a bomb. Smaller lumps skittered down the cliff from above, one forcing her to jerk aside to avoid it. Harhund and the other mercenaries faced the same danger, Martel taking a blow from a falling chunk and almost slipping from the ledge. ‘Get to the boats!’ Harhund roared.

He and Martel resumed as quickly as they dared. Roche started towards Nina – who remained defiantly still. ‘What are you doing?’ he yelled, stopping four feet away. ‘Move, you stupid bitch!’

‘Fuck you, asshole!’ the New Yorker shouted back. ‘Just climb past me! I’m going back to the fortress!’

‘The hell you are!’ He fumbled to unshoulder his MCX. Even in its short-barrelled model, the rifle was still awkward to manoeuvre at such close quarters. ‘Move or I shoot you!’

‘Whoever hired you needs me alive, moron! Think you’ll get paid if you kill the only person who can make that thing work?’ She jabbed a thumb towards the pouch containing the key.

Roche looked down as if he had forgotten it was there, then his eyes flicked after Wintz’s departed boat. ‘They’ll have the coffin, they’ll have the key,’ he said. ‘Two out of three ain’t bad.’

He aimed the SIG at her chest—

The cavern rocked again, a great swell of water smashing into the cliff’s foot.

Both Nina and Roche were thrown against the wall. The iceberg continued its roll, metal groaning above as the hanging Dionysius was brought almost overhead. Nina gripped the ropes, flattening herself against the ice – which she realised with shock was now nearly thirty degrees from the vertical. The fortress would soon be on the level – would it stop when it got there?

The thought vaporised in the face of danger as Roche recovered. His expression was one of near-panic, self-preservation his only concern – and she was the biggest obstacle in his way. He brought the gun up again—

A whoosh from behind – and the Dionysius’s swinging anchor smashed into him with the force of an artillery shell.

August reached the corridor’s end, spotting the opening and shining his light inside. Two figures were huddled together, nowhere to go. His finger went to the trigger—

Running footsteps, rapidly closing. He glanced back, expecting to see one of his comrades – but instead saw Eddie Chase charging at him with something in his outstretched hand.