Rosie is a little girl with big worries. Today is her sixth birthday, and she is having a party at the space museum with all her friends. She loves everything about space... but she cannot stop worrying about all of the things that might go wrong. What if nobody comes to her party? What if it's too loud? What if it's scary? Her 'worry whisperer' often twists her tummy into knots with questions like this.

This is the story of how Rosie begins her journey to accept and love her worry whisperer for what it is – a protector that sometimes does its job a little too well. Sometimes, Rosie discovers, she can be brave too.