It's the start of a new term at the School of the Good Sisters and Hanna, Edie and Calla are ready to enjoy everything their extraordinary school has to offer. But they soon realise that Something Is Most Definitely Up. Not only is a mean businessman trying to open a kale factory in Little Hampden and remove all their delicious snacks, but their beloved Headmistress Good Sister June has disappeared - and nobody knows where she's gone.

It's time for Hanna and her friends to rally an army of first years to protest against the horrors of kale while they set out on an adventure to bring Good Sister June home. As they travel across the country following a trail of clues, they will learn about the power of family, friendship, and a well-timed slice of Victoria Sponge...