“The bridge is moving. So am I!” Ark winced. As they reached the other end, Mucum put his fingers to his lips. Even from outside the door, they could hear the snoring. A sign, etched in stark brown and white into the grain, said:

EFFLUENT EXECUTIVE STATION
EMPLOYEES ONLY BEYOND THIS POINT.

Underneath, someone had scribbled, Wot is the point? It’s all a load of … The last word had been crisscrossed out with a knife.

Ark frowned. “Are you sure about this? Why don’t you go in?”

“You worry too much, mate! The patter of little footsteps won’t wake the old man, I promise.”

Mucum eased the handle and they crept in. The room spread before them resembled an enormous and rather smelly kitchen, though it wasn’t food that was on the menu here. Various pipes and mini aqueducts wound their way through the roofs and walls to discharge into two huge troughs that ran the length of the shed. These bubbled away, releasing their noxious gases in the first stage of composting. Large wooden paddles turned the muck slowly, worked by winches and a series of cogs and chains that ran all the way up to sails far above the crown of the tree.

The troughs had color-coded depth levels marked up the side. If the level went too high, for instance when a bout of diarrhea hit, an alarm went off. Jobby Jones, their line manager, would then run about screaming: “Incoming! Incoming!” and happily leave it to the plumbers to bail out the troughs into what was called “overflow” — a big hole in the floor. The rest of it, once composted, was sent along pipes through the forest all the way up to the high scaffields for the crops that Dendrans relied on.

It wasn’t the best system in the world, but it worked and it gave them all a living of sorts. Jobby Jones ruled this under-crown empire with a fist of oak, when he could be bothered. Today, at least, his bulbous body was happily ensconced on the daybed in the corner, his twitching nose no doubt dreaming of perfume that only the richest could afford.

Little Squirt was curled up on the floor next to the nearest trough, grabbing a moment’s peace. It was his task to remove any blockages and help the general flow. Being a squit stirrer wasn’t the best job in the world, but someone had to do it.

“Hey!” whispered Mucum. “Over here!” He motioned to the tool closet, but Ark was drawn to an old bird’s-eye map pinned up on the wall and covered in familiar stains.