Mirabelle is special because she is different. Her mum is a witch and her dad is a fairy and she LOVES getting up to magical mischief. So, her parents' picnic party in the garden seems the perfect chance to play some pranks on her annoying brother, Wilbur. But when Mirabelle gets caught putting frogspawn in Wilbur's drink she's sent inside. It's so unfair! Why should she have to miss the party? Then a brilliant idea strikes: If she uses a shrinking potion on herself, she'll be too tiny for anyone to see, so she'll still be able to enjoy the party! But Mirabelle is about to discover that the garden feels a little more dangerous when you're no taller than a blade of grass. Have her mischievous ways gone too far this time . . . ?