The Thea Sisters is a group of five female mice from all over the world. One of them is Colette, who is from France, and it is because of her that the group visits Paris. While on their vacation in the city, they visit the fashion school where Colette had studied, and they meet her friend, Julie.
Julie is a successful designer and is taking part in a fashion show. But, just before the show, someone steals her entire collection. The Thea Sisters decide to help her find the dresses and Colette goes undercover to find who stole them.
The adventure takes the five friends all across Paris as they desperately try to find the culprit, and recover the collection in time for Julie to be able to take part in the show.
As is usual with all the Stilton series books, the story is not just entertaining but informative too. There are special sidebars throughout the book with information on France, Paris, and many aspects of French culture.