During World War II, the United States sent soldier Harry Cook to Norway to help a scientist defect from Nazi Germany while working on the atomic bomb. Once captured and imprisoned in a high alpine castle on the German-Swiss border, Cook must devise a plan to escape with the scientist before the Gestapo uncovers his true identity. With the help of other prisoners, they build a two-person glider to fly to safety in Switzerland, racing against time before being caught by the Germans or the Gestapo.