Further down the tree, sapsmiths were draining amber-coloured liquid from taps set into the bark. They poured it into vats and buckets, down pipes and chutes that led to the factories and breweries below, where it would be used to make potions and syrups, mead and ale. They left a cloud of sweet, sticky scent in the air that gummed up Liska’s whiskers as she sailed through.

Everywhere there were crowds of tiny figures going about their business, but no sign at all of the hulking treekeepers.

Round the outside of the tree she flew, passing over the colossal roots as they grew over one another in endless twining layers. Where temples, libraries and workshops balanced among them in clusters. She saw the arbomancer Academy, the printing workshops of the stormsinger scribes, the hanging gardens of the mossherders . . . sights and wonders everywhere she looked.

Further still, she came to Undren Square – a wide open space between the smallest roots and the beginning of the first tree circle that was used for gatherings and ceremonies.

Night was beginning to draw on and it was mostly empty now. Just a few figures clustered at the edge. Two mages and . . . was that a treekeeper with them?

Liska flew closer, gliding down until she was ten metres or so from the ground. She flew under the lowest of the tree’s branches, where it was dark and cool. Clusters of hanging lanterns – each one larger than her own bedroom at home – cast pools of warm, yellow light on the forest floor and the air was thick with the spicy scent of magic.

It was a treekeeper! With long, thick legs, gnarled and carved with spirals. With an ivy beard that almost reached the ground. Strings of green glowing runes ran up and down its arms, matching the gleam of its deep-set eyes. Magic poured out around it in an aura that Liska could almost see, almost taste.

It looked like Edda – the oldest, most important of the Keepers. Liska recognised him from brief glimpses she had caught before.

Gliding silently, she drifted closer, circling around to try and see what was so important that Edda himself had come down from his palace on the tree.

As she passed around the edge of the square, she could see Edda stooping downwards, talking to a man in long, sweeping robes of black and silver. An arbomancer. An important one, judging by the amount of symbols embroidered on his cloak. He was waving his hands wildly and snatches of a raised voice drifted towards Liska’s sharp, fox ears.

Someone was daring to shout at a treekeeper? She had to get closer. She had to find out more.