Fashion is in ten-year-old Gemma Riley's DNA. Raised by her grandmother, the famous fashion designer Cara Bonafete, Gemma rushes from school each day to the House of Bonafete and then into the design room - her favourite place in the whole world. While running errands for her grandmother and watching the pattern-makers and machinists at work, she dreams of one day creating her own collection. But there's big trouble in the House. The date for the showing of the new Spring Collection is looming, Cara has fallen and broken her wrists, and someone is stealing their designs. With ingenuity, pluck and a sewing bag at hand, it's up to Gemma Riley to solve the mystery and save the fashion day.