Mitchell’s footprints stood out clear and sharp in the dust, and Saul followed them along the lunar surface, in long strides that would have been impossible back on Earth. He looked ahead and saw tvantage.ed straight to the rim of hills, a few kilometres away. He breathed evenly as he ran, pacing himself and keeping his eye out for any loose rocks that might trip him. He recalled reading somewhere that the close proximity of the lunar horizon made it hard to judge distances.

‘Mitchell!’ he yelled over the A/V. ‘Can you hear me? Mitchell!’

No answer.

The most economical way to run on the Moon, he knew from previous visits to Copernicus, was a kind of lope that fell just shy of skipping. It exhausted him all the same, so that when he came to a halt, about halfway towards the hills, the inside of his suit already reeked of stale sweat. The terrain had meanwhile taken on a different texture, the regolith giving way to ripples of ancient lava and boulders left over from the time when part of the crater wall had collapsed, aeons before. This made it a lot harder to pick out Mitchell’s footsteps.

‘I just want to know what the hell’s going on,’ Saul shouted again over the A/V. ‘You owe me that much.’

‘Do I?’ came the unexpected reply.

Saul straightened up, still panting from his exertions, and stared over towards the hills. If Mitchell was there somewhere, he couldn’t see him. He tried zooming in with his contacts, but there was so much debris scattered everywhere, it would be easy for Mitchell to hide himself amongst it.

‘I know there’s some connection between you and those artefacts,’ Saul gasped. ‘Olivia found the proof: this all started when they brought you back from Site 17.’

‘What’s happening now,’ said Mitchell, ‘is too important to let you, or anyone else, interfere.’

Saul could tell from the sound of the man’s breathing that he had also been running. So he started moving again and, after another few minutes of steady progress, he spotted movement amongst the deep shadows cast over the base of one of the hills. He squinted intently, till one of those shadows resolved itself into a tunnel mouth cut into the side of a hill. Saul stopped, exhausted, and sucked water through a straw located inside his helmet.

He looked around and saw he had come to the edge of an old construction road. Rubble was piled into mounds by the roadside, while several abandoned-looking construction vehicles and a broken-down mobile foundry stood nearby, stark and black against the stars. He started running again, gradually picking up his pace.

‘You were never actually going to help me shut down the Array, were you?’