Briefgeheim (2010)

Secret Letter tells about 11-year old Eva, who's fed up with all the tensions at home. In order to make her parents clear how she feels about this, she runs away from home. She hides in the attic of her best friend's place, Jackie en Thomas. When she finds a secret letter and gets caught in neighbor Brandsema's garden, the head of a criminal organization, her plans take an unexpected turn