Just as time seemed to run out, the Atn started to slide forward, slowly at first, and then with increasing speed. It scraped against the stone floor and then collided with the facing wall. They stumbled after it, using their hands to try and steer it away from either side.

As the spiders finished their programmed burn, the Atn kept moving forward under its own momentum, dead limbs flailing as it drifted up from the floor and towards the ceiling, turning slowly as it went.

‘Don’t let it get turned around too far!’ Nancy yelled. ‘If it gets wrapped up in the cables, it’ll pull the spiders in towards it.’

The Atn smashed into the ceiling and lost some of its momentum. At least, Ty thought, they had it moving in the right direction. It scraped grit and dust from one wall as it drifted onwards.

‘Okay,’ said Ty. ‘Second burn, now.’

He tapped at his arm console and triggered the second blast of energy. The spiders shot towards the mouth of the shaft, drawing the cables taut once more, and dragging the Atn’s lifeless form after them.

The second burn seemed to last for ever.

The spiders finally ran out of fuel, and the cables grew slack once more as the Atn drifted forward, colliding with the three spiders and grinding one of them to pieces against a hard surface. Smashed components and delicate robot arms were sent flying, but it was heading in the right direction. A few seconds later the alien’s body finally sailed out into the main shaft, spinning slowly and followed by a hail of fresh debris and machine parts.

Several spiders had been hovering nearby, and their programmed sense of self-preservation made them scatter like fish disturbed by a shark as the Atn went crashing into the main shaft’s opposite wall. It then rebounded at a fraction of its original velocity, tangled in cables, from the spiders still tethered to it.

Ty looked up along the shaft towards the external entrance and saw a ring of stars surrounding the bulky silhouette of the fast launcher. A cable extended down from it, its tip swaying just a few metres above them.

He grinned: Cesar had clearly been hard at work. Ty pushed himself towards the cable and grabbed hold of it.

The Atn kept rotating slowly, more or less hanging in the centre of the shaft. Ty managed to cling to one of its legs long enough to secure the cable to it. He pulled himself on top of the Atn, then opened a link to Cesar.

‘Nathan,’ came the response. ‘How’s it going down there? Are we ready to move?’

‘Yeah,’ Ty replied. ‘Start pulling it in right now.’