Edie was born to a family of troublemakers. When her activist parents leave Paris to protest around the globe, her grandmother decides it's time she became a proper young lady and so sends her to the School of the Good Sisters. But to Edie's surprise, the nuns at the school teach genuinely useful things, like how to build a perfect library, cater for midnight feasts and make poison darts, and mischievous Edie feels right at home. When a school trip to Paris is planned, she worries about returning to the strict order of her grandmother's chateau - but things are not as she left them. Soon Edie and her rebellious friends are caught up in a mystery involving a precious painting, secrets from her grandmother's past and a very persistent burglar...
