No sign of the Torrox – but there was another ship, rust-streaked white above a grimy black hull. The sarcophagus was being brought aboard by a foredeck crane. He could just about read the ship’s name: Tahatu? It sounded Indonesian, or Maori.

He frowned. Even if they started the Dionysius’s engine, they didn’t dare leave the cave. There were at least two armed mercenaries on the other ship, maybe more—

A loud, crackling boom made him flinch. He spun, seeing broken ice fall from a huge new crack extending from the ancient ship to the hole in the ceiling where the Dionysius had been trapped.

Imka was almost at the bottom of the cliff, Cheng clumsily following her down. The student cried out as a chunk struck him, and lost his hold on the rope. He skidded down the slope, yelling all the way, and was about to slither straight into the water when Imka grabbed him and brought him to a halt just short of the sloshing edge.

Nina let out a relieved breath. ‘God, I thought he was going in.’

‘He’ll have to go in anyway,’ Eddie pointed out.

Imka helped Cheng up, then retrieved the life vests. She donned hers, and offered the other to him – only for him to hold up his hands in rejection, instead taking off his backpack. ‘What’s he doing?’ Eddie asked in disbelief. He shouted across the water. ‘Leave the bloody bag and put your vest on!’

Cheng shook his head, saying something to Imka that produced a nod of understanding. She gave him her own life vest before carefully tying his bulging backpack on top of the other. Eddie stared in angry bewilderment. ‘No, just leave it! Don’t— Oh for fuck’s sake!’ Imka jumped into the water, gasping with the shock of the cold before waving for Cheng to follow. He did so, letting out a stifled shriek as the freezing sea swilled over him. Imka started to pull him towards the Dionysius, Cheng towing his pack on top of the flotation device.

More icy fragments skittered down the cliff in their wake. Another echoing crack came from above as a new fault line zigzagged upwards from the fortress. A car-sized lump of ice plunged from it, slamming down on the shimmering metal hull – with a flare of light.

Nina’s eyes snapped to it. It hadn’t been caused by sparks; rather, the strange iridescent glow seemed to have reacted to the impact. To her surprise, the metal was undented despite being hit by a ton of frozen water.

The fortress had not escaped unscathed, though. The impact was transmitted through the rest of the structure – and part of the ice wall trapping it began to crumble.

With a tearing crunch, the fortress started to grind loose of its prison.