"Original English language edition first published in Great Britain 2016 under the title 'The mystery of jewelled moth' by Egmont UK Limited"--Title page verso.
Summary
Our heroines, Sophie and Lil, don cunning disguises, mingle in high society and munch many cucumber sandwiches to solve this curious case. Applaud their bravery as they follow a trail of terrible secrets that leads straight to London's most dangerous criminal mastermind, and put their own lives at risk. It will be the most thrilling event of the season.