It consisted of little more than an open chassis mounted on a set of bulbous wheels. A man in the drivers seat, his face half hidden by a breather mask, nodded a greeting to Malcolm.

Malcolm pushed her into a bucket seat in the rear before climbing in next to the nameless driver. Strap in, he instructed her, in case we have to make a break for it.

The car slowly drove out from between the two warehouses, then headed straight for the gate. Two large steel-plate doors slid apart automatically at their approach.

Sirens began to sound through the night air, echoing off the face of the massive cliff. The sliding doors suddenly came to a halt, then began to close again, fast.

Go, yelled Malcolm, grabbing his companions shoulder. The vehicle shot forward, accelerating hard. It spun to a halt on the other side of the gate, having only narrowly avoided being sliced in two.

Close, said Malcolms friend grimly. Malcolm merely nodded, looking shaken.

They got under way once more, rapidly picking up speed. They were soon racing downhill along a nearly deserted access road, with the sound of sirens still wailing behind them. At the bottom of the hill, a city brilliant with light stretched out before them. Beyond it she could just make out the dark expanse of a mighty river or ocean.

Something buzzed overhead, shining a light down onto the road ahead. Their driver reacted by swerving violently into steep undergrowth, sending the vehicle crashing and bouncing down a vertiginous slope at such speed that Dakota felt sure it would flip over and crush them beneath its weight. Instead they bounced out onto a switchback road level with the rooftops of what looked like residential buildings situated near the base of the hill.

The driver swerved again, and suddenly they were passing along a narrow street. Dakota saw businesses and homes on either side, the machine that had buzzed them probably a drone of some kind now lost in a haze of light and noise.

The driver wove through another series of tight turns, before taking them down a steep ramp leading underground. Passing through an atmospheric containment field, they entered a brightly lit space that was broad and big and busy enough to constitute a whole subterranean city in itself.

Dakota pulled her mask down and breathed in air that tasted of sweat and smoke and a thousand other flavours that made her very, very glad still to be alive. After the freezing temperatures of the Redstone night, this underground community felt shockingly warm. She even began to sweat under her heavy coat.

Malcolms friend had barely slowed down. They careened along a thoroughfare with a bustling open market on either side, huge stone-and-steel pillars supporting the city streets above ground. Dazzlingly colourful images shifted and morphed above a warren of stalls and businesses.