Ark sprinted toward the last car and hopped onto the mineral express. No turning back now. Within seconds, he was enveloped in total darkness. The gloom soon faded as they arrived at a tipping station. Each car was balanced at either end on a huge axle. The cars ahead began to slowly tip over to the left, pulled by a giant magnet at the side, to spill their load into an overgrown box on the side of the track. This container was attached at each corner to a four-way hoist. When the box was full, the ropes went taut and the cargo began to lift. Box after box slid up in smooth transit and was swallowed by the blackness above. Although Ark strained his eyes, they couldn’t pierce the shadows.

Never mind. This was a free ride and saved him having to take the stairs, all five thousand of them. His legs had never been so grateful. The only problem was how to avoid being flattened by a few hundred tons of industrial ore. Ark scrambled over to the right-hand side of the car and held tightly on to the edge as it began to lean over. Soon, as he gripped tight, his legs were dangling in the air and his nose filled with dust. He desperately tried not to sneeze, in case there were any Rootshooters around. At the very last moment, and with a quick prayer to Diana, he closed his eyes and let go.

There was a bump and Ark felt a piece of rock scrape his shin, hard. He tried not to cry out as he dared to open his eyes. He had made it, perched on top of the mound of ore, inside the box as it slowly rose up to the ceiling. There was an awful screeching noise and the ceiling split in two, like a pair of giant hinged trapdoors, filling the cavern with the smells of … earth. As the box swayed slightly from side to side and slowly slipped from the safety of the cavern, Ark crawled to the edge and peered over.

“Flipping fungus!” The familiar tree trunk on his left was not the reason why he nearly fell off in shock. He was horrified, then fascinated to see the ground itself, not thirty feet below him, spreading out from the roots like a soily brown scaffield. The Holly Woodsmen said that the earth was unclean. Nobody who left Arborium to climb down had ever returned to tell the tale. And yet this place didn’t look dangerous. The smell was loamy, deep, and pleasant.

An animal, nibbling on vegetation, looked up to see a brown face staring back.