During the 1943 German occupation of Denmark, 10-year-old Annemarie Johansen and her family take great risks to give shelter to Annemarie's best friend, a Jewish girl named Ellen Rosen. Ellen assumes the identity of Annemarie's sister, but the Nazis are suspicious of this dark-haired girl in a family of blondes. As the Nazis move closer to discovering Ellen's true identity, Annemarie must find the courage to go on a dangerous mission that will help Ellen escape from Denmark.