Bianca ran all the way back to the park. She couldn’t tell if it was her imagination or because she was running, but it felt like the further she got from the four strange children, the warmer it became. Her mind was a blizzard of questions, whirling and dancing, so that she couldn’t focus on any one thing or catch any answers.

Who were they? What were they doing? Why were they going about the city pretending to be a man? What was wrong with that kid’s hand? Where had the glass in the windows come from?

Bianca knew she’d been gone for a long time and was worried her parents had woken up and discovered she was missing. They were so distressed about Finn; she didn’t want to make it worse. When she finally stumbled into the rose garden, breathless and worn out, she was relieved to find her parents still fast asleep on the bench. A gentle snore was rising from her father’s lips.

Taking the spare sleeping bag from the tent, Bianca climbed into it and wriggled under her dad’s arm. She could hear his heart beating. It was a comforting sound. It soothed the frightened thoughts that buffeted her brain. As she warmed up, her eyes closed, and her breath fell into sync with her father’s.

‘Bianca, my love, wake up,’ her dad called softly, and she floated out of darkness. ‘Mum’s going to take you home.’

Bianca blinked her eyes open, remembering she was in the park. The sky was the colour of mushrooms, the dawning sun obscured by the thick snow clouds. Her legs were stiff. It was very cold. She saw a frill of frost on the rose bushes. Her mum helped her to her feet and a police officer escorted them out of the park and into a car, before driving them home.

Taking her straight up to her bedroom, Bianca’s mum tenderly removed her boots and tucked her into her bed fully dressed.

‘Sophie and Casper have been frozen, Mum,’ Bianca mumbled. ‘They’re from my school.’

‘The police officer told me,’ her mum replied in a whisper. ‘It’s not safe for you to be in the park, Bianca. That’s why I’ve brought you home. Now, get some sleep.’

Bianca knew that nowhere was safe. Hadn’t Finn been stolen from his own bed? But she didn’t say this. She just nodded and closed her eyes, allowing the warmth of her own bed to envelop her.

The deathly pale Jack, with the snowflake hand and needle teeth, was waiting for her in her dreams, holding out a sparkling silver book. But every time she reached for it, it was whipped away and the wind laughed at her.

When Bianca awoke, she had a fire in her belly. Today she was going to get her hands on one of those silver books even if it killed her. Tomorrow she would have to go to school and there would be no time to investigate. She pulled her boots back on and clattered down the stairs.

Her mum was already up. She was sitting at the kitchen table drinking coffee. ‘What would you like for breakfast?’ she asked Bianca brightly. ‘I’ve made banana bread.’ One glance around the room told Bianca that her mother had been cleaning for hours. Everything shone like new, and the room smelt of lemons.

‘You baked banana bread?’

‘Yes. I couldn’t sleep.’ Her mother looked into her coffee cup, which she was turning nervously in her hands. ‘I didn’t know what else to do.’

Bianca sat down, reaching for her mum’s hand. ‘I’m going to work out who did this to Finn, and Casper and Sophie, and then I’m going to find a way to unfreeze them.’

‘You don’t need to do that.’ Her mum gave her a watery smile. ‘You just keep yourself safe, Bianca. Don’t go talking to strangers. The police are taking things much more seriously now that two more children are . . . in the park.’

‘But I’ve got a lead. It’s something to do with the silver book. Finn and Sophie both had one. I’ll bet Casper did too.’

‘Bianca, books can change what people think, and touch their hearts, but I don’t see how they can freeze a person.’ Her mother got to her feet. ‘Now, how about I toast a slice of that banana bread for you and cover it in butter?’

Bianca nodded. She wasn’t going to argue with her mum. As she ate her breakfast, she made lots of appreciative noises and praised her mother’s baking, but it barely raised a smile.

‘If you’re going back to the park,’ Bianca said, licking the melted butter from her fingers, ‘can I go to the library? Mrs Dorcas will look after me, and it’s cold in the park.’

‘I don’t see why not.’ Her mum cleared away her plate. ‘I’d feel happier knowing you were in a safe place.’

When Bianca opened the front door, the air that rushed to greet her was so cold that it stung to breathe in. There were two bottles of milk standing on her doorstep. Picking one up, she shook it. The creamy contents didn’t move. It was frozen. Winter has the power to transform a liquid into a solid, she thought, and found her mind leaping to an image of her brother and her friends in the park. Her throat tightened and her eyes prickled as a sudden wave of fear and sadness threatened to overwhelm her. She shook herself, shoving the bottles on the hall table, inside the house, and closing the door roughly. She patted her coat pocket, checking her diary and pen were inside. She must concentrate on her investigation.

A neighbour was scraping frost off the windscreen of his car and talking to a woman a few doors down.

‘Did you hear? Two more were discovered last night!’ he said.

Bianca drew back into the porch, listening to their conversation.

‘That’s three children frozen now,’ replied the woman.

‘Yes! I mean, what are we supposed to do?’

‘My sister’s taking her children out of the city.’

‘But the Christmas holidays are coming.’

‘It’s not safe here.’

‘You think more children will be frozen?’

‘Almost certainly.’

‘What kind of a monster targets children!’ the man exclaimed.

‘I heard that the mayor has called for volunteers to patrol the streets at night. My Ron is joining up.’

‘I hope they catch whoever is doing this soon.’ The man opened his car door, signalling he had to go.

As Bianca walked down the path, she felt the woman staring at her.

I wish it would hurry up and snow, she thought, fastening her coat and putting on her gloves, ignoring the gawping neighbour. The ground was treacherously icy. She half walked, half slid to the library, losing her balance several times, but managing to catch herself before she fell.

Bianca had decided that as soon as she got hold of a silver book, she would take it to the police station and explain her theory, that it was somehow linked to the frozen children. The book was evidence.

No, it’s not evidence, she thought suddenly. It’s a weapon! She stopped walking as a worrying thought crossed her mind. Or is it a trap? What if she found a book and it imprisoned her in ice? Surely she would be able to resist its spell because she knew what it was. But what if she couldn’t? Would she be frozen too?

‘I won’t read it,’ she told herself, continuing on her way. ‘I can’t help Finn if I’m an ice statue.’

But what if it wasn’t the reading that got you? What if it was looking at the pictures? Or maybe you didn’t even need to look inside. What if just holding the book trapped you?

When I find one, I won’t touch it, Bianca thought, looking at her gloved hands. I’ll keep my gloves on, put the book into a bag and wrap it up tight. She always carried a folded-up bag in her pocket, for picking up other people’s litter.

When she got to the library, Bianca found the giant wooden doors closed. She tried the handle. They were locked. She saw the sign beside the door, CLOSED ON SUNDAY, and her heart sank. She’d been so caught up in events that she’d forgotten the library didn’t open today.

She dropped down, sitting on the steps, the wind gone from her sails. At least, she consoled herself, if the library is closed, no one can get a silver book today.

No silver books meant no more frozen children.

But it didn’t help Finn. He’d been frozen for two nights now. How long could he remain that way and survive? She immediately shook the horrible thought from her head. She mustn’t think like that. Instead, she thought about the four strange children she’d seen last night at the factory. She suspected they had something to do with the silver books, although none of them had been carrying one. But she remembered the victorious smile on Jack’s face at the sight of poor frozen Casper. She was certain they had something to do with that.

A girl with a pixie crop and a wide smile skipped past the library steps. Bianca sprang to her feet. The girl was holding on to her mother’s hand and under her other arm she was carrying a silver book.

Recognizing her as Gwen Olsen, who often played with Finn in the park, Bianca called out, running after her.

‘Gwen, wait!’

Her mother stopped and turned. When she saw who’d called her daughter, her expression changed to a pitying smile. ‘Bianca!’

Having learned her lesson with Sophie, Bianca darted forward and grabbed the silver book under Gwen’s arm. She yanked it away.

But Gwen had been gripping the book tightly. When Bianca yanked it, she pulled Gwen off her feet. As she fell, Gwen yelped and knocked the book from Bianca’s hands. She threw herself on top of the book on the pavement. ‘It’s mine!’

‘Bianca!’ Gwen’s mum looked shocked. ‘What on earth are you doing?’

‘You mustn’t let her read that book!’ Bianca cried. ‘It’s dangerous.’ She turned to the five-year-old girl. ‘Gwen,’ she said, trying to soften her voice, as if talking to a frightened cat. ‘You know me. I’m Finn’s sister.’ Gwen’s eyes grew wide. ‘Did you hear what happened to him?’

‘He got turned into ice,’ Gwen replied.

‘Finn had a silver book like yours. He read it on the day he was frozen. That book is a trap. I think that if you read it you will turn into ice too.’

‘That’s enough, Bianca!’ Gwen’s mother stepped protectively in front of her wide-eyed daughter. ‘You’re scaring her.’

Gwen hugged the glinting book to her chest, a feverish look in her eyes.

‘I’m sorry about what happened to your brother,’ Mrs Olsen said, ‘but you can’t go around frightening little children. Everyone is scared enough as it is. If you want a book so badly, then go to the bookseller in the market – he’s got a box of them. It’s where Gwen got hers.’

‘What I’m saying about the book is true, Mrs Olsen! You must believe me. Please don’t let Gwen read it. Please!’

The number 73 pulled up at the library bus stop. Mrs Olsen grabbed her daughter and ushered her on board, clearly in a hurry to get away from Bianca. As the doors closed, Gwen waved, but Bianca was already running towards the market square.

She sprinted past the cathedral. Its bells were ringing to signal the end of morning service. She sped by City Hall and arrived gasping in the square. There was a market every weekend. On Saturdays it was a food market, with fresh fruit, veggies, fish and meat, but on Sunday it was antiques, curiosities, old clothes and second-hand books.

The market traders were wrapped up in thick coats and scarves. Gloved hands clutched steaming cups of coffee. There weren’t many people shopping. It was too cold.

Bianca spotted three trestle tables stacked with books. A short man wearing a flat cap and waxed jacket stood beside it.

‘Excuse me,’ Bianca said, approaching him. ‘Are you the bookseller?’

‘Indeed I am, young miss.’

‘I’m looking for a book.’

‘What’s it called?’

‘I don’t know, but it’s got a silver cover.’

‘Do you know how many people think I’ll know which book they’re talking about if they just tell me the colour of the cover?’ He chuckled. ‘I’ll need a bit more to go on than that. Who’s it by?’

‘I don’t know, but you sold a copy to a five-year-old girl just now. She has short brown hair.’

‘I didn’t! I haven’t made a sale all morning. It’s too frosty for people to take off their gloves and reach into their wallets.’

‘But her mother said you had a box of books,’ Bianca cried. ‘She said . . .’

‘Oh! Them!’ The bookseller pointed to a cardboard box on the floor. ‘She must have taken it from there.’

Under the table was a box with a sign pinned to the side saying FREE BOOKS FOR CHILDREN. Bianca dropped to her knees and rummaged through it.

‘There isn’t anything worth much in there, but, if a child likes something, their grown-up usually feels obliged to buy a book off the table.’ The bookseller sounded pleased with his clever ruse.

‘Did you put a silver book in here?’ Bianca asked, riffling through tatty board books, comics and dog-eared paperbacks, her heart slowly sinking.

‘I don’t think so, but, if I’m honest, I don’t pay much attention to the box until it’s looking empty.’

Bianca drew back. There were only ordinary books in the box. It struck her as odd that there was a scattering of hailstones under the table, but her desperate search drove all other thoughts from her head. She was too late. Once again, the mysterious silver book had eluded her.