They dived over a ridge just as the ship’s bow sliced past right behind, half burying them in a cascade of frozen rubble. The Dionysius hit the water, kicking up a massive wave. It rolled almost to the point of capsizing before swinging back upright. A crane on its aft deck collapsed and slumped over the gunwales like a broken-necked giraffe, the funnel toppling after it with a hollow crash.

Nina clawed her way out of the broken ice and stared in disbelief at the rocking ship. ‘Oh my God! We made it!’

‘We’ve still got to get out of here,’ Eddie reminded her, a hand to his temple where he had been struck by debris. ‘Christ, my head hurts. Got any ice?’

‘Ho h— Oh shit.’ She looked past the Dionysius to see the wave it had thrown up pound against the cavern’s far wall . . . and rebound back at them.

This time it was Eddie’s turn to pull her with him. They scrambled away from the water’s edge, but the smashed surface turned every step into a nightmare. The wave grew louder—

And hit them.

They were both swept up the slope by the freezing water – then dragged away by the backwash as it retreated. Nina gasped as the deathly chill penetrated her clothing. She fought desperately to keep her head above the surface, only to be slapped by choking breakers of salty froth. All she could do was try to stay upright until the wild ride eased.

She heard her name being shouted. ‘Eddie!’ she replied, spitting out seawater and searching for him. She belatedly realised she had lost the pouch containing the golden key, but that was now the least of her worries. ‘Where are you?’

‘Over here!’ His voice came from the direction of the Dionysius. He was out of the water, on the mangled crane arm. ‘Swim over here and climb up!’

Despite the draining cold and the still-turbulent water, she managed to make her way to the ship and hook an arm over the metal frame. ‘Oh God! I’m freezing!’ she gasped.

‘Get out of the water, then we’ll worry about warming up.’ He helped her over the gunwale and they huddled together, shivering on the frost-covered deck. The ship’s superstructure had been damaged by the fall, skewed sideways and every window smashed. ‘What the hell just happened?’

‘I don’t know,’ Nina replied as she fumbled to remove her crampons, ‘but it’s all to do with that.’ She indicated the fortress – then spotted something bobbing amongst the broken ice below. ‘And that.’

Eddie saw the floating yellow pouch. ‘Suppose you’ll want me to get that for you?’ he grumbled.

‘Normally I’d say yes, but it’s not at the top of my priorities list. Where are Cheng and Imka?’