‘Over here.’ She aimed her light at a panel beside a line of large grey cylinders, each the size of a bathtub. Steel hoses ran from valves to the engine. She tapped at a glass-fronted pressure gauge before turning a handle below it. Air thrummed through the pipes, the gauge’s needle springing up.

‘Will it work?’ Eddie asked.

She pursed her lips. ‘It might. But there isn’t much air in the tanks. And the engine’s cold; there’s no way to pre-heat it. It might have seized up.’

‘We’ve got to try,’ he insisted. ‘Otherwise we’ll freeze – or get shot. Anything I can do to help?’

She pointed at a console. ‘That’s for engine control. The ship’s pointing away from the cave entrance, so I need you to set it to reverse. Oh!’ she added as he started towards it. ‘And the turning gear interlock has to be disengaged. It’s on the other side of the engine, a red valve.’

‘Bit dark,’ he said, rounding the block to see only shadows.

‘Sorry.’ She joined him and aimed the light at a protruding cylinder. ‘There. Open it as far as you can.’

He started to turn the valve as she returned to the air tanks. ‘You really know your way around a ship.’

‘My dad was an engineer in the South African navy. I studied marine engineering at university. That was where I met Arnold, actually . . .’ The moment of brightness at the thought of her fiancé quickly vanished.

‘I’m sorry,’ Eddie said quietly.

‘Arnold . . . Arnold was inside the . . . the UFO when the ceiling fell in. There’s nothing left, he’s gone . . .’ Her voice quavered.

He kept turning the valve. ‘Imka. Imka! I know this is bad, but I need you. You’re the only one who can start the engine. Keep your mind on that – tell me what to do.’ The interlock reached its limit; he stopped, waiting for her response. When none came, he continued, more forcefully: ‘Imka. The valve’s open – now what?’

‘The . . . the engine control,’ she managed to say. ‘There are two dials with speeds marked on them. The one on the left, set it to slow astern.’

He picked his way across the oil-smeared floor to the console, just able to read the controls in the wash of her light. He turned the left-hand dial one notch anticlockwise, bringing a marker needle to the first position in a red zone: the ship’s reverse speeds. ‘Done.’

‘Okay. I’ll set the valves to put air into the first cylinder. If there’s fuel in the system, it’ll ignite when the cylinder reaches maximum compression and start the cycle.’

‘Will it work without the batteries?’

As with Cheng a few minutes earlier, there was a hint of condescension in her words. ‘It’s a diesel engine – it doesn’t need spark plugs.’