‘It most certainly isn’t “nothing”,’ said Ambrose. ‘You warriors risk your lives for us all the time. Don’t think that it’s not appreciated . . . no matter how some of us may act.’

He nodded at Liska, and then walked back to the classroom, leaving her to rub her sore shoulders, bruised where the vines had squeezed them.

‘Flukes and nematodes,’ said a quiet voice next to her. ‘That was close.’ Liska had forgotten about the brown-robed boy. He was still standing there, blinking at her with his puppy-dog eyes. His hands were still trembling and a tiny vein had started to twitch on his forehead.

‘Thanks for trying to help me,’ she said. ‘But I had the whole thing under control.’

‘Oh, did you?’ said the boy. ‘Because it looked a bit like Odis and his friends had you trapped and were about to kill you. Anyone who even mentions his father is risking their life.’

‘So, the shouty mage was his father? That figures. I’m Liska, by the way.’ She held out a hand, expecting him to grasp her wrist in a warrior handshake. Instead he took hold of her fingertips and gave them a tiny wiggle. It was a bit like shaking hands with a breeze.

‘I’m Lug,’ he said. ‘Pleased to meet you. You’re the first shapewalker I’ve seen. Up close, that is.’

‘What type of tree wizard are you, then?’ Liska asked. ‘I didn’t know there were any who wore brown robes.’

Lug sighed a little as he answered. ‘I’m a vermispex,’ he said. ‘There aren’t very many of us. And we’re not very . . . well known.’

Liska raised an eyebrow. This was something she’d never heard of before. ‘What’s your power?’

Lug blushed. For a moment Liska thought he wasn’t going to tell her, but then he knelt and tapped on the ground as if he were knocking at a door. When he stood again, there was a plump, glistening earthworm coiled on the palm of his hand.

He began to waggle his fingers and the worm reared up, waving its head from side to side like a snake-charmed cobra. Then it wound itself into a ball and began to roll around. Finally, Lug knelt back down and released it. The poor thing hastily buried itself in the soil, disappearing from sight.

‘Worms,’ said Lug. ‘We summon and control the worms in the soil of Arborven. They keep the earth fresh and full of food for the trees, you know. Without us, the city would probably shrivel up and die. You’d think everyone would appreciate that a bit more. But they don’t.’

‘So, do you have a circle to live in? How close to the tree is it?’

‘Well,’ Lug began to squirm. ‘It’s not a circle exactly. And it’s probably not as close as it could be. In fact, it’s quite far away. Behind . . . behind the mossherders.’