Zoe’s troubles began on the way home from school. Most of the kids caught the school bus from the main gates, but the bus didn’t go past Zoe’s house. Instead, she walked through the playground to where her little brother, Max, was in kindergarten.

Usually Max was annoyingly bouncy, as if he hadn’t seen Zoe in a year. But today he slumped against the railings of the school fence as they waited for Mum. It was a warm afternoon and he had his jumper on, but he was still shivering.

‘Can I borrow your jumper, Zoe?’ he asked, sounding miserable.

Zoe was searching in her bag when her mum drove up.

‘Hurry up, Zoe,’ her mum called out the window. ‘Can you help Max with his bag? It looks too heavy for him today.’

Zoe dumped both bags into the car and jumped in behind them. Max dragged his feet over to the car, looking more tired and sad than ever.

‘Max!’ said her mum. ‘Your teeth are chattering! Zoe, what’s wrong with your brother?’

Zoe sighed and shrugged.

Sometimes it was a pain being the big sister. She wanted to talk to her mum about Isabelle, and whether she could have her and Iris over, but now all her mum’s attention was on Max.

By dinnertime, Max’s chill had turned into a fever. By breakfast the next morning, he was covered in spots.

‘Chickenpox!’ said her mum. ‘How are you feeling, Zoe? Any spots?’

‘I’m fine,’ said Zoe, impatiently. ‘I just want to get to school.’

Her mum didn’t seem to notice that Zoe was in a hurry. ‘Go and get dressed then,’ she said calmly. ‘I’ll have to make a few calls before we go anywhere.’

Zoe dressed as quickly as she could while her mum was on the phone. She was just sliding her favourite ladybug hairclips into place when her mum came in.

‘Bad news, Zoe,’ she said. ‘I called Dr Ho to get a medical certificate for my work, so I can take time off to look after Max –’

Zoe nodded.

‘And Dr Ho says you’ll have to stay home, too.’

‘What?’ gasped Zoe. ‘But I’m not even sick! Please, Mum, I have to be there today. Can’t I – ’

‘No,’ said her mum, firmly. ‘You haven’t had chickenpox yet, so there’s about a 90 per cent chance you’ve got it now. Dr Ho says the spots could appear any day.’

‘But couldn’t I go until I get sick?’ asked Zoe.

‘I’m sorry, Zoe. Even though you don’t feel sick yet, you could still pass it on to others. You can’t go to school. And no visitors, either. It’s just you, Dad, me and Max.’