With the rise of the Berlin Wall, twelve-year-old Gerta finds her family divided overnight. She, her mother, and her brother Fritz live on the eastern side, controlled by the Soviets. Her father and middle brother, who had gone west in search of work, cannot return home. Gerta knows it is dangerous to watch the wall, to think forbidden thoughts of freedom, yet she can't help herself. She sees the East German soldiers with their guns trained on their own citizens; she, her family, her neighbors and friends are prisoners in their own city.
But one day, while on her way to school, Gerta spots her father on a viewing platform on the western side, pantomiming a peculiar dance. Then, when she receives a mysterious drawing, Gerta puts two and two together and concludes that her father wants Gerta and Fritz to tunnel beneath the wall, out of East Berlin. However, if they are caught, the consequences will be deadly. No one can be trusted. Will Gerta and her family find their way to freedom?