Stella Starflake Pearl decided she did not like the courthouse in Coldgate one bit.

Not only was it a looming, imposing, ugly building, with high ceilings, paintings of serious-looking, disapproving judges and stone statues of justice griffins everywhere, but the people who worked there were stiff and serious and seemed to have their collars buttoned up too tight. Perhaps that’s why the staff all had that sweating, slightly throttled look – including the panel sitting behind the bench.

The panel consisted of the Polar Bear Explorers’ Club’s president, Algernon Augustus Fogg, along with three other retired explorers. They were all men, grey-haired, with disapproving expressions that caused their moustaches to bristle from time to time. They all stared down accusingly at Stella’s father, Felix, who stood alone before them, dressed in his pale blue explorer’s cloak.

The courthouse was normally used for putting criminals on trial, but the Polar Bear Explorers’ Club were allowed to use it for occasions like this, when one of their members was under investigation for rule breaking. Felix had, unfortunately, broken quite a few rules recently when he mounted an unauthorised expedition to Witch Mountain. And Stella and her junior explorer friends  – Shay, Ethan and Beanie  – had done the same when they followed him in case he needed rescuing.

This was the third time she and Felix had been to the courthouse now, and it seemed to Stella that the place had been specially designed to make you feel insignificant and small. The very air – thick with a long history of disagreements and arguments and misery and grievances – made Stella feel all twitchy and itchy inside her clothes. Most of all, she hated the fact that they were treating Felix like some kind of criminal. It was so unspeakably unfair. Yes, he may have broken a few rules, and he may have gone to Witch Mountain against the wishes of the Polar Bear Explorers’ Club, but it had all been a matter of life and limb, and any explorer ought to be able to understand that.

Stella adjusted her position on the chair and tried to persuade Mustafah, Hermina, Humphrey and Harriet to settle down in her lap. Unbeknown to her, the four jungle fairies she’d met on their last adventure had stowed away in her pockets when they left home, and she was quite concerned they might get into mischief. She’d already caught Hermina, with her catapult out, aiming a stink-berry at one of the brooding stone griffins adorning the walls.

The other people in the courthouse kept throwing disapproving looks at them too  – the jungle fairies kind of stood out with their green skin, leaf tunics and impressive blue spiky hair. And while there wasn’t a rule against fairies being inside the courthouse as such, it was certainly the case that the building had a dry, life-sucking air – probably on account of all the lawyers – and that it felt somehow wrong for something as magical and marvellous as a fairy to be there.

It was now three weeks since the fairies had returned with Stella and her friends from their fateful expedition and all the trouble had started. Felix and Stella had both found themselves on trial for rule breaking and now their very membership of the club hung in the balance. After two visits to the courthouse, last week they had received a telegram informing them this would be the final meeting and that a decision would be reached by the end of the day. Stella saw that everyone had come to see the result, including the president of the Jungle Cat Explorers’ Club and his odious son, Gideon Galahad Smythe. Shay, Ethan and Beanie were there too, along with Beanie’s mum, Joss, a slender elf with long blue hair and pointed ears.

Stella was shocked to see her friends. Today was Beanie’s birthday and he had been planning his party for ages. When Stella found out they were due to appear in court, she’d sent a messenger fairy with a note saying she couldn’t come. She had assumed the party would go ahead without her, yet here they all were in this horrible place instead.

Shay, the wolf whisperer, caught Stella’s eye and waved at her from across the aisle. It was warm and stuffy inside the courtroom, and yet Shay was still wearing his cloak and seemed to clutch it to him, as if in need of the warmth. Stella raised her hand back, trying not to show her stab of unease at the sight of the white streak in Shay’s hair. Had it got a little bigger since she’d last seen him, or was it her imagination? Either way, there was no time to lose.

Koa, Shay’s shadow wolf, had been bitten by a witch wolf just as they were leaving Witch Mountain, and Shay would almost certainly turn into a witch wolf himself if they didn’t do something to help him. But they had tried everything they could, with no success. The only possible chance to save Shay was to travel over the cursed Black Ice Bridge – a forsaken place that no explorer had ever managed to cross. Somewhere on the other side was a mysterious person called the Collector, who had stolen Stella’s birth mother’s Book of Frost, which contained a spell that might save Shay’s life. But it was a formidable task – most said impossible – and they ought to be finishing their preparations for it, not be stuck in this stupid courtroom wasting their time. Stella couldn’t help gritting her teeth in frustration.

‘You knew the club did not want you to go to Witch Mountain,’ one of the old explorers on the panel was saying to Felix. ‘And yet you went anyway.’

‘Is that a question, Nathaniel?’ Felix asked mildly.

‘This is your final chance to offer some explanation or justification for your behaviour,’ the explorer replied.

‘There are some things in this world that are even more important than the Polar Bear Explorers’ Club,’ Felix replied. ‘As I have already told this court, I went to Witch Mountain because I believed there was a witch there who meant my daughter harm. I feared for her life.’

President Fogg’s mouth went into a thin, straight line, but he shuffled some papers around on the bench in front of him, peered down at the top sheet, then looked back at Felix and said, ‘You have taken full responsibility for your adopted daughter  – the ice princess known as Stella Starflake Pearl – and you do not deny that she broke into the Polar Bear Explorers’ Club and stole a valuable artefact—’

‘I deny both those points, sir,’ Felix interrupted sharply. ‘Vehemently. As a junior member of the club, Stella should never have been denied access in the first place. Furthermore, the artefact she took was a tiara that belonged to her and was only on loan to the club temporarily. It’s not possible to steal your own property—’

‘What about my dirigible?’ cried a voice from the other side of the courtroom. Stella turned and saw that the speaker was Wendell Winterton Smythe, the president of the Jungle Cat Explorers’ Club. ‘You’re not going to argue that belonged to the girl too? And what about my son? He was magically assaulted.’

‘I’m the one who assaulted him!’ Stella’s friend, Ethan Edward Rook, rose to his feet, scowling. His black Ocean Squid Explorers’ Club cloak gleamed beneath the sickly glow of the courthouse lights. ‘It wasn’t Stella; it was me. And I’d do it again too. In a heartbeat!’

Unfortunately, Gideon Galahad Smythe had been on board the dirigible when the young explorers had used it to flee from the guards at the Polar Bear Explorers’ Club. He was a few years older than them, and very handsome, rude and mean. To their dismay, he had tried to sabotage their rescue attempt by turning the dirigible back around. So Ethan had used his powers as a magician to transform him into a wonky squish-squish frog and he’d spent most of the expedition stuffed inside someone’s pocket.

Stella knew that Ethan had not really acted properly there. He should have turned Gideon back into a boy the moment they arrived at Witch Mountain, but the magician claimed to have forgotten the spell. The others had all known deep down that this wasn’t true, but no one had tried very hard to persuade him to turn Gideon back because they had evil witches to worry about, and vampire trolls and ice spiders, and no one particularly wanted to listen to him complaining while they attempted to scale the mountain.

Stella could still see the pure hatred that had blazed in Gideon’s eyes as he’d glared up at Ethan from where he lay sprawled on the salted planks of the pier after they got home and he was human once again.

‘I’ ll get you back,’ he’d said. ‘One day, I swear I’ ll get you back for what you did to me.’

And now here he was, making life difficult for them. If Gideon hadn’t been so furious about the whole thing, perhaps the president of the Jungle Cat Explorers’ Club might not have made such vociferous complaints, and this might all be going very differently now.

Gideon stood up from his chair, completely ignored Ethan and addressed the judge instead. ‘The magician had nothing to do with it,’ he said. ‘He’s just trying to take the blame for the ice princess. No doubt she’s bewitched him somehow.’ He pointed at Stella....