10-year-old Agathe-Christine will be a detective. He wants to solve puzzles now. Time for the first "real" case. Catching a mysterious thief from a local shop is just a matter of time.

Skirt, jacket, tie, broad-brimmed hat - you can see at once that Agathe-Christine is a detective. When he moves with his family to a new city, he immediately sets up a detective office, and in the local shop he gets the first real order: he has seven days to discover who makes a minor theft. He's got a suspect right away! She is sure that it is Vincent - an eternally grumpy and mysterious boy from the neighborhood. But sometimes appearances are wrong, and the first trail does not have to be the right one. Can a detective puzzle be an opportunity to get a real friend?