Gadreel lurked at the side of the arch with a couple of his men. All were armed, but they were hanging back from the fight. Nina saw why as one warrior peered through the opening – only to fall backwards when a sniper’s bullet punched straight through him with an explosive spout of blood. Cheng swore in Chinese. ‘What’s that English saying about frying pans?’ he asked.

‘Getting out of them into the fire?’

‘Yes – except the fire is also surrounded by men with machine guns!’

‘We’ve got to get past them somehow,’ Nina said firmly. ‘It’s the only way out of here – and Macy’s over there.’

‘We still have to get down this path first.’ He looked over the edge – only to hurriedly pull back with a gasp.

‘Vertigo?’

‘Yes, yes.’ He wiped his sweating brow. ‘Somehow I forgot I had it. My brain reminded me!’

‘Just stay on the inside and don’t look down.’ She promptly ignored her own advice to see what lay below. Zan was nowhere in sight; he had presumably reached the bottom of the spiral and entered the lower chamber. His armoured chaperone ran across the bridge to join Gadreel.

‘Zan made it down,’ she reported before continuing. ‘He must have taken the tracker to Sidona.’

‘Why does she need it?’ he asked. ‘She’s already started the attack.’

‘Maybe they can use it to revive the rest of their people more quickly.’ She made another turn around the spiral – then abruptly halted. ‘Oh, crap!’

‘What is it?’ Cheng asked.

‘There’s a big-ass hole in the walkway!’

A chunk of the path had been torn away by the fallen bridge, only twisted stubs of the support struts remaining. The gap was over ten feet wide. Cheng paled. ‘How are we going to get across?’

‘Either jump, or climb down.’ She went to the ragged edge. The next leg of the spiral was more than fifteen feet below. Lowering herself as far as she could before letting go would cut the fall to eight or nine feet – manageable, but any stumble on landing could send her over. On the other hand, the path’s curvature around the pillar provided a very limited landing area if she jumped the gap.

She didn’t like either option, but the first seemed marginally less risky. ‘I’m going to drop down.’

‘Are you sure?’

‘You’d rather jump?’

‘No! I . . . I don’t want to do either.’

‘Nor do I, but I’ve got to stop Sidona.’ Nina lowered herself over the edge. A glance down to check she was lined up with her landing site – then she let go.

She dropped, the crystal pillar flashing past her—

Her feet hit the metal floor with a jarring bang. She gasped, reeling towards the endless drop below – before throwing herself back at the pillar. ‘Professor!’ cried Cheng. ‘Are you okay?’

‘Yeah,’ she said, straightening shakily. ‘Okay, your turn.’