Billie runs out into the playground. Jack mooches along behind her.

‘I can’t believe it!’ says Billie. ‘I got a solo!’

All the kids in the playground stand around Billie and cheer for her.

Jack can see that Billie is happy. He wants to be happy too.

But right now he just feels cross. It was his idea to try out for a solo in the school concert. Not Billie’s!

Jack scrunches up his face and kicks the ground.

He feels a big dark monster inside him grumbling to be let out.

‘It’s only a stupid school concert!’ Jack shouts. ‘Who wants to sing a solo anyway? Only stupid people!’

Billie turns to Jack. Her mouth drops open and her eyes grow wide.

‘Jack!’ she says. ‘That’s mean!’

Jack knows it’s mean. But he can’t help it. It’s the big grumpy monster talking, not him.

Jack runs away from Billie to the other end of the playground.

For the rest of the day, Jack and Billie don’t speak to each other. Jack glares at Billie and she glares back.

Jack wants Billie to say sorry. He doesn’t know why.

It’s not fair that she got a solo in the school concert and he didn’t.

But soon the grumpy monster in Jack’s tummy goes away. He knows it is up to him to say sorry.

‘I’m sorry for being mean,’ he says. ‘I’m happy that you got a solo, Billie. Really. Friends?’

‘Friends,’ Billie says, smiling. ‘Forever.’

‘Hey, maybe you can help me practise my solo?’ Billie adds.

Jack nods. ‘Sure,’ he says. ‘I’d like that.’

All that week and the next, Jack helps Billie practise her solo for the musical.

They sing everywhere. In the kitchen and in the bathroom. In the garden and in the house.

They sing as loud as rock stars — except when it’s time for Billie’s baby brother to have a nap. Then they sing baby Noah to sleep.

Jack can’t wait for the concert!