Cheng reached the ledge, relieved to have something other than steel spikes beneath his feet. He began the traverse, conspicuously not looking down. Imka appeared around the pillar behind him. Eddie watched with disapproval. ‘Don’t really want more than one person coming across at a time.’

‘Won’t the ropes take it?’

‘I’d rather not find out. Imka!’ he shouted. She paused. ‘Wait until he’s over here before getting on to the ledge.’

‘I can’t just hang on here!’ she protested.

Eddie frowned. Amateurs becoming impatient was a recipe for trouble. ‘At least let him get past that piece of metal.’

‘Cheng, the ice is loose there,’ Nina warned. ‘Be very careful.’

He clutched the screw and swung around the ratchet. ‘I’ll be fine—’

The ice burst apart beneath his right boot.

He flailed his leg, trying to regain his foothold – and the crampon came off, flapping from his heel on its strap.

Cheng squawked in surprise and instinctively shifted his weight to regain his balance. His other foot slipped from the ledge. He fell—

The ropes caught him.

For a moment. Then one of the ice screws burst free.

Cheng screamed as he dropped again—

The other screws on each side held. He jerked to a halt three feet below the ledge. Gasping, he flailed at the wall, gloved hands struggling for purchase on the smooth surface.

Eddie was already moving back across the cliff. There wasn’t time to clip his harness to the rope; instead he simply gripped it as he half walked, half leapt along the ledge. ‘Cheng, I’m coming!’

The student was becoming panicked. ‘Cheng!’ Nina shouted. ‘Use your foot, dig the crampon into the ice! No, not that foot,’ she added almost with a disbelieving eye-roll as he kicked at the ice with his right foot, the loose crampon flapping beneath it. ‘The one with the spikes!’

He made another attempt, this time with the fully attached crampon. Metal bit into the surface. That secured him just enough for him to raise himself. One hand found a hold on the ledge. He shouted in Mandarin, straining to bring himself up.

‘I’ll be there in a second!’ Eddie yelled. ‘Try and get hold with your other hand!’

The student did so, fingers clutching the edge. Eddie hopped sidelong to the nearest screw holding Cheng’s weight. The ice around it had turned opaque under the strain, crackling and squealing. He wrapped his right arm around the rope leading back across the cliff, then took hold of the length supporting Cheng and pulled. ‘Can you get your foot any higher?’

Cheng made a face of extreme effort. ‘I . . . yes, yes, I can,’ he said, inching upwards.