11-year-old Eva, frustrated with tensions at home, runs away and hides in her best friend's attic. Her disappearance aims to convey her feelings to her parents while seeking refuge with Jackie and Thomas.

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 and 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.—lemming film