With the rise of the Berlin Wall, twelve-year-old Gerta finds her family suddenly divided. 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. 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.