Pookiecrag Castle wasn’t as haunted as the townsfolk of Dundoodle believed it to be, but the children were still grateful they wouldn’t have to visit it in the dark. Its ruins loomed over them ominously as the magical boat carried them over the loch to the castle’s island home. Fliss didn’t seem to mind too much. She spent the journey focused on the star-shaped toy, trying to work out how to open it, whilst Archie stood at the prow, wondering if Jings would be able to help them. But Billy shivered in his seat miserably. He hugged Sherbet, who had joined them in the vessel along with the little honey dragon, Blossom.

‘It’s like the old bones of a giant,’ he whispered in the dog’s ear, looking up at the crumbled stone walls, as the boat drew alongside the castle’s jetty. ‘A corpse of a building, waiting to rise from the dead and terrify the life out of all the poor little sheds and bungalows in the neighbourhood.’

‘It can’t always have been creepy,’ said Archie, nimbly jumping out. ‘It was once a family home. Belle McBudge’s home.’

‘Do you think she might have left the Treeheart here?’ said Fliss. ‘Perhaps she gave it to the honey dragons for safe-keeping.’

‘That’s what I’m hoping,’ replied Archie. ‘Then we could get this business over with quickly.’

The entrance to the Cavern of Honeystone was hidden behind a trapdoor in the fireplace of the castle’s great hall. It opened on to a long tunnel that led right into the heart of Ben Doodle mountain. There, in a cave filled with a forest of golden honeystone crystals, lived the dragons. The children arrived to find them busily making new crystals from the nectar they had collected earlier in the day. The cavern was filled with little blasts of fire and glassy, pinging sounds as the dragons spat out fresh honeystone on to the stone floor.

‘It’s a bit dangerous in here!’ said Billy with a yelp, ducking as a newly formed molten crystal flew past his ear and ricocheted off the wall.

In the centre of the cavern, Old Jings was settling himself down in his nest. The biggest and oldest of the dragons, he was the only one who still knew how to use human speech. Blossom flew up to him, and squeaked a smoky ‘Hello’. Old Jings chuckled.

‘Well, I never!’ he said. ‘Honey dragons learning the mortal tongue once more! You human folk are making quite an impression, for ones so young.’ However, his scaly face lost its cheer when he heard why the children had come to see him. The dragon’s golden eyes glistened with emotion at the news.

‘So the Mirk is back!’ he muttered. ‘I’ve heard rumours of sightings. I hoped we might have seen the last of that foul being, after Belle McBudge dealt with it.’

‘What happened?’ asked Archie. ‘Do you know what she did with the Treeheart afterwards?’

‘I don’t,’ growled Old Jings. ‘She would not speak of it, nor of what had occurred – it was too terrible. For on that cursed Unquiet Night, we lost one of our own. It was the last time a honey dragon died in violence, and the Mirk was responsible!’

As the dragon shook with rage, the children looked at each other in horror. What a horrible notion – the honey dragons were such friendly little creatures! What if something happened to Blossom? It didn’t bear thinking about.

‘We lived much more closely with humans then,’ Old Jings continued. ‘The McBudges were still in Pookiecrag Castle, so we saw them often. Belle had her own favourite dragon, just like you, girl. It went everywhere with her, but that was its downfall. All Belle could say was that it had spent its last fire defending her and the Wyrdie Tree. Her heart was broken.’

Archie thought of the dragon statue in Belle’s portrait. It must have been a memorial to her lost friend. He could feel the dread and fear worming their way into his mind again.

‘What is the Mirk?’ asked Billy. ‘Is there anything you know that might help us?

‘It is an entity of darkness. A forest spirit. Once, it was a terrible tree whose branches spread like black tentacles, causing destruction and decay.’

‘The Mirkthorn!’ said Archie, remembering Miss Clabbity’s story.

‘The roots of the Mirkthorn tapped into the same earth magic that is the source of the power of the Wyrdie Tree, but twisted it to evil purposes. The dragons destroyed the Mirkthorn tree, burning it with our magical breath. And that should have been the end of it. But somehow, through some dark enchantment, the tree’s spirit survived. As a shapeless dark monster, it attacked the Wyrdie Tree to drain the forest magic for itself, but Belle defeated it.’

‘We’ve seen it,’ said Archie. ‘The Mirk. In the forest. It was cloaked, but we could tell it was something to be afraid of.’

‘It must have been in hiding for many years whilst it bided its time for another chance to strike at the Wyrdie Tree.’

‘And we’re still no closer to finding a way to stop it!’ said Billy.

‘Perhaps …’ said the dragon. It claws rummaged amongst the untidy stack of crystals that made up its nest, picking up and discarding various random objects it must have collected over the centuries – biscuit tins, broken toys, rusty tools, snow globes. Eventually, it produced an old book. ‘The journal of Archibelle McBudge. Whilst she did not leave us the Treeheart, she entrusted us with this. It might be important in your search.’

Old Jings handed the book to Archie.

‘Good luck, Guardian,’ he called, as they left the cavern. ‘The honey dragons will come to your aid, when the time comes.’

The sun was turning a hazy orange when they emerged from the tunnel into the long shadows of the castle. Blossom sat on Sherbet’s back as the dog led them back through the ruins to the jetty.

‘I’ll get straight to work on reading the journal,’ said Billy eagerly, as he clambered back into the boat. ‘There must be some clues in there – there’s no other reason Belle would have wanted the dragons to look after it.’

‘We’ll meet up again on Sunday – assuming I survive the party tomorrow,’ said Archie. He looked around. ‘Hang on, what happened to Fliss?’

She was nowhere to be seen. Then, after a moment, she emerged from the castle, looking a little dazed.

‘Where were you?’ asked Billy. ‘Are you all right?’

‘I … tripped on a stone,’ she said uncertainly. ‘I’m fine.’ She got into the boat and seemed to shake off her confusion. ‘Let’s get going,’ she said firmly.

She looked her normal self, but Archie noticed she had the strange cold look in her eye he had seen earlier. And he didn’t like it.