‘Sophie! Wait!’ Bianca called out, and was immediately shushed by other people in the library. She sprinted to catch up with the girl, keeping her eyes glued firmly on the silver book.

‘Hi, Bianca,’ Sophie said as they passed through the library doors together and came out onto the stone steps.

Sophie was an athletic girl with long honey-coloured hair and a cheeky grin. She wasn’t in the same class as Bianca, but they were both in the school netball team. Sophie was the captain and played centre. She was a natural leader, outgoing and kind.

‘Where did you get that book?’ Bianca asked, her hand reaching towards it.

‘The library,’ Sophie replied. ‘Why?’

‘I’ve been looking for it all morning,’ Bianca said. ‘Can I see it?’

‘No.’ Sophie stepped away from Bianca, moving the book so it was behind her back.

‘I only want to look at it.’

‘This is my book.’ Sophie narrowed her eyes, and Bianca was startled by her cold expression. Sophie was usually so generous and friendly.

Bianca took a step back. ‘I just want to know the name of the book and who it’s by. My brother brought it home yesterday—’

‘Go away!’ Sophie shouted, pivoting, clutching the book to her chest. ‘It’s mine. You can’t have it.’ And she ran, jumping down the last two steps, and sprinted away.

Bianca was shocked. She had never seen Sophie behave like this. She thought about running after her, but Sophie was fast. And what would Bianca do if she caught up? Try to take the book from her? Sophie was clearly not going to let it go. Bianca remembered seeing a similar look on Finn’s face when she’d asked to see his book last night. That was what had started their fight.

Sitting down on the steps, Bianca took her orange diary from her pocket and wrote down what had happened. How was it that Sophie had found a copy of the book when Bianca had looked everywhere for it? Had she missed a shelf? Where had Sophie found it? And why wouldn’t she let her look at it? Bianca was beginning to suspect that this was no ordinary book.

Rising to her feet and crossing the road, Bianca entered the park, taking the route through the rock garden and past the boating lake to the rose garden. Her stomach clenched at the thought of seeing Finn in the light of day. Last night he had seemed peaceful, almost magical, but she feared that, in the daylight, she might see signs of distress.

When she arrived at the entrance to the rose garden, an opening in the hedgerow, she was alarmed to see it was blocked by people. She heard her dad call out her name as she pushed through the crowd. A police officer, a young man, helped her through a barrier of yellow tape that had been put in place to keep back the curious onlookers.

Her mum was standing beside Finn, gently rubbing his frozen arms. She was wearing her sheepskin jacket and a blue bobble hat. Tendrils of her auburn hair coiled down her back like skinny snakes. Bianca was struck once again by how angelic her little brother looked on his pedestal of ice. He glowed with a gentle blue light. It was clear that her parents’ attempts to thaw him had failed.

There was a newspaper on the ground beside the park bench where her mum and dad had put their bags. The front-page headline read: The Ice Child! Bianca picked it up and scanned the short article. It didn’t name Finn, but it reported where he was in the city park. She spotted copies clutched by several people in the crowd and felt a wave of anger. Did they think this was a freak show? Had they all come to gawp at her brother, the ice child?

She felt an arm round her shoulder and looked up into her mum’s brown eyes.

‘You’re wearing the jumper I made you?’ Her mum tried to smile.

‘I love it,’ Bianca replied fiercely.

‘Come and sit with me on the bench.’

They sat down together, and Bianca noticed her mum’s nose was pink from the cold.

‘Are you all right?’ her mum asked.

‘Are you all right?’ Bianca replied.

‘No,’ her mum admitted, chewing her bottom lip.

‘Me neither.’

‘I wish I knew what to tell you.’ Her mother sighed and Bianca saw her eyes fill with tears. ‘I don’t understand what’s happening.’

They looked at Finn for a long moment.

‘Mum, can I ask you about Finn’s bedtime last night?’

‘I’ve been over it with the police, and with your father.’

‘I need to hear what happened.’ Bianca swallowed. ‘I never got to say goodnight to him. We had that fight, remember? You sent me to my room . . .’ She fell silent.

‘Oh, Bianca. I’m sorry.’ Her mother looked down. ‘Let’s see. I told Finn to get into his pyjamas and clean his teeth at seven o’clock. When he was done, he said goodnight to Dad, and then I tucked him up in bed. He was hugging Sposh. Then I read him a story, kissed his forehead, turned on his nightlight and turned off the main light.’

‘Do you remember which story you read Finn?’ Bianca leaned close.

‘Erm . . . now let me see.’

‘Was it from the silver book he brought back from the library?’

‘Do you know . . .’ Bianca’s mother frowned. ‘I’m not sure if I did read to him. I thought I had . . .’ Her bottom lip trembled.

‘I’m sure you did,’ Bianca tried to reassure her.

‘But maybe I didn’t. I mean, I can’t have read him a story if I don’t remember the book, can I?’

‘The shock has probably made you forget,’ Bianca said, feeling the hairs rise on the back of her neck. ‘I don’t suppose you know where Finn’s library book is, do you?’

Her mother shook her head, looking perplexed.

Bianca knew her mum had a good memory. If she lost her gym socks, or Dad lost his keys, Mum always knew where they were. It was odd that she couldn’t remember reading to Finn.

Lunch was a round of sandwiches brought to them by the police. Bianca ate hers sitting at Finn’s feet, staring up at him, willing him to move.

‘Twitch your fingers if you can hear me,’ she told him, but Finn didn’t move a frozen muscle. She tried everything she could think of to make him respond. She told him he’d left Sposh at home, and that the rabbit missed him. She told him that if he moved they could go home and play Bonky Smash, a raucous game they’d invented when he was three, where they’d bounce on their parents’ bed trying to knock each other down onto the mattress. Eventually Bianca fell silent. Nothing worked.

Dinner was a takeaway and, as it grew darker and colder, the gawking crowds silently filtered away. Bianca’s dad suggested they all go home and get some rest, but her mum wouldn’t hear of it. ‘What if Finn wakes up and I’m not here? He’ll be scared,’ she pointed out. ‘I’m not leaving. You can take Bianca home.’

‘But I can’t leave you here alone all night.’

‘We’ll all stay,’ Bianca said firmly. ‘I don’t want to go home without Finn.’

Sleeping bags and a small tent appeared from somewhere. Bianca’s dad pitched the tent beside the bench and insisted her mum get into a sleeping bag and try to get some sleep. Mum curled up on the park bench using Dad’s lap as her pillow. She said she wouldn’t be able to sleep and wanted to watch over Finn.

Bianca climbed into the tent and took out her diary, scribbling down the strange details of her mother’s failure to remember Finn’s book. She felt frustrated. The book was the only lead she had, and she hadn’t learned anything about it. Tomorrow, she would go to Sophie Lilley’s house and beg to see it.

As it got late, Bianca’s eyes grew heavy. Realizing she could barely keep them open, she wriggled into a sleeping bag and positioned herself so she could see Finn through the tent flaps.

The chimes of midnight from the City Hall clock echoed across the park and woke Bianca. For a moment she was confused, but the sight of Finn through the tent door orientated her. She felt a stirring in the air and scrambled out of her sleeping bag. As she emerged from the tent, she fancied she heard the wind chuckling like a naughty child. Her pulse quickened. Something was wrong.

She spotted a woman running along the path beside the rose garden.

‘Where are you going?’ Bianca called out.

‘They’ve found another child,’ the woman replied without stopping. ‘Another ice child.’

Bianca gasped, turning to her parents. They were both fast asleep on the bench, her dad slumped down over her mum. She grabbed her sleeping bag and gently covered her father. It was bitingly cold.

‘I have to go,’ she whispered to their sleeping faces. ‘It could help Finn. I won’t be long.’ And with that she ran, heading in the direction the woman had been going. She saw a gaggle of people around the bandstand and sprinted towards them as fast as she could.

In the middle of the bandstand, standing on a pedestal of ice, was a girl in a nightshirt and shorts, a waterfall of honey hair down her back. Her arms were crossed, her eyes closed and she had a happy grin on her pale frozen face. It was Sophie Lilley.