It was huge, towering over the rest of the forest. Archie thought he could see clouds grazing its uppermost heights. A mountain of yellow, gold and red, the Wyrdie Tree’s canopy sprawled around a swirling mass of branches, some wide enough to support a house. Are those windows twinkling amongst the leaves? Archie could imagine an entire city of tree houses hidden up there.

As they walked into its dappled shadow, he could sense the weight of its magic, but this magic wasn’t oppressive or full of dread. It wrapped around and comforted him, like a blanket on a cold day. He walked up to the massive trunk and pressed his hand against its bark. From deep within the wood, a rumble juddered through Archie’s fingertips. Was the Tree welcoming him?

Billy dropped his rucksack on the grass and pulled out his black notebook. He began busily sketching the standing stones.

‘There’s so much to record for my book,’ he said. ‘I’ve got loads of questions. Is the stone circle some sort of celestial clock? Do the shadows cast by the stones tell you when to perform some important, ancient ritual?’

‘Sort of,’ said a voice from the branches above. A figure jumped down from the tree, landing on the grass in front of them. ‘We use it for our washing-up rota.’

Two more figures appeared on either side of the first. It was the little men they had met the day before! They were dressed the same, in their green hoods and leaf-covered cloaks. One had the robin perched on his head, another the red squirrel on his shoulder, and the third carried Ingeborg the mole. It seemed to be the only way to tell them apart. Sherbet ran up to them, sniffing suspiciously.

‘When you’ve been here as long as we have,’ the first man said, as the robin gave Sherbet an aloof chirrup, ‘it’s easy to forget whose turn it is to do the dishes.’

‘How long have you been here?’ Archie asked. ‘And who are you?’

‘We came here with her, when she was but a sapling,’ said another of the men, gesturing at the Tree. ‘We sailed from the Fjord of Fjurge, in the far northlands beyond the sea, many, many years ago. Our ship was crewed by the Viking Trolls of Fjurgeholm, charged with protecting their precious cargo.’

‘The Fearsome Vikings of Fjurge!’ said Billy. ‘There are legends about their savage and destructive reputation in Dundoodle – knocking over flowerpots, stealing laundry, chasing cats and generally being very impolite.’

‘The Tree was planted here?’ said Archie. It looked like it had stood there for hundreds, if not thousands, of years. The men nodded.

‘She is but a child of the original Tree,’ said one, ‘the World Tree that grew between the domain of men and the realm of the old gods. It was home to magical creatures and its roots even reached down into the hidden, underground lands of the dead. When the World Tree was threatened by war between the gods and giants, a seed was taken and grown in the world of mortals to preserve some of its power. The young tree-child was carried to safety over the sea and planted here in secret.’

‘We, the Fjurge Brownies, have tended her ever since,’ continued another of the men. ‘I am Jøkchip, and these are my brothers Jøknut and Dubbeljøk.’

‘You’re brownies!’ said Billy. ‘I thought you might be gnomes, like the notorious Dimpledrumpskin, who made you guess his name because he was too embarrassed to tell you himself.’

The Fjurge Brownies looked indignant.

‘Gnomes, indeed!’ snapped Jøknut, making the robin hop about fretfully. ‘Useless creatures! Good for nothing but kitchens, or sitting on toadstools, fishing in ponds. Brownies are helpful household folk, but the Fjurge Brownies have specialised in gardening and horticulture.’

‘Then why does the Wyrdie Tree need a Guardian?’ said Fliss, looking at Archie. ‘If you three are here with your spades and watering cans all the time.’

‘The Guardian protects the magic of the Tree,’ said Dubbeljøk. ‘Your wyrdworking powers are needed, young McBudge. That’s why she has summoned you. Her leaves are changing colour. Last week she was entirely green. It is a sign.’

‘But I don’t have any powers,’ said Archie. ‘At least, I don’t think so. They haven’t developed yet.’

The brownies looked at each other worriedly.

‘That we should have a mere boy, at such a time,’ muttered Jøknut to his brothers.

‘What?’ said Archie. ‘What do you mean?’ He didn’t like being called a ‘mere boy’. It sounded like the dismissive kind of thing Mrs Puddingham-Pye would say.

‘It is the time of Renewal,’ explained Jøkchip. ‘The Wyrdie Tree only sheds her leaves every five hundred years. They change from green to gold, then to red, before falling on Unquiet Night.’

He put Ingeborg the mole down on the ground and walked up to the base of the Tree, to where the bark formed into a diamond-shaped notch.

‘On that night the Guardian takes the Treeheart – the ancient Jewel of Renewal, a crystal fruit from the mother World Tree – and places it here. The Wyrdie Tree immediately sprouts new leaves, and with them comes a renewal of her powers. The wyrdie-folk celebrate with their Dance of the Wyrd, but during the time when her branches are bare, the Tree’s power is reduced and she is vulnerable.’

‘Vulnerable to what?’ said Fliss. ‘Magical greenfly?’

‘Attack!’ said Dubbeljøk, his eyebrows wrestling each other into a frown that was bushier than the tail of his pet squirrel. ‘There are those who would harm the tree and take her magic for themselves.’

‘Mrs Puddingham-Pye?’ said Billy.

‘Maybe,’ said Archie. ‘Or do you mean the Mirk?’

The brothers trembled.

‘The Mirk is an ancient forest spirit of darkness,’ said Jøknut. ‘Its greatest desire is to control the Tree, turning her heart black, whilst stealing her power like a parasite. It has already tried once before – at the last Renewal.’

‘When Archibelle McBudge was the Guardian!’ said Archie. ‘That was the last time the Tree sent out a summons.’

‘And she was successful,’ said Dubbeljøk. ‘The Mirk had overpowered us, imprisoning us in a dark cloud of swarming flies. Using her wyrdworking knowledge, Belle was able to cast the evil spirit out of the forest. She saved the Wyrdie Tree! But we fear the Mirk has returned.’

‘I think we might have seen it,’ said Archie. ‘On our way here, we hid from a horrible … thing. It looked like a person, but it wasn’t. I could sense its power.’

‘It must have taken some kind of human form!’ said Dubbeljøk, turning pale. ‘We suspected as much. But you say you could sense it? That means your wyrdworking powers are developing. You are sensitive to strong magic … but that means it can sense you, as well.

‘And then we found the cut-down trees,’ said Fliss sadly. ‘Or at least, what was left of them.’

‘We have heard rumours from the forest-folk – the dryads, the moss-goblins and the brook-babblers – of trees disappearing,’ said Jøkchip, scratching his beard, which seemed to be made from moss as much as hair. ‘Some of the missing trees are enchanted. The forest is like the Wyrdie Tree’s family, the trees all gain strength from each other. Attacking the forest could be the Mirk’s attempt to weaken the Tree further. It failed to take control of the Tree once before. This time, it will do everything it can to succeed.’

‘Fear the Mirk!’ said Jøknut. ‘It is ravenous, relentless and filled with cunning. If it has hidden itself amongst man, it will be whispering its malice, and darkening hearts of those around you. It won’t stop until it has what it wants. All things fear its hunger for power!’

‘So we need this Treeheart-Jewel thing,’ said Archie, frowning. ‘Where is it?’

‘We were hoping you could tell us,’ said Jøkchip mournfully. ‘The Jewel of Renewal is lost!’