It's 1940 and World War II is underway. In Sheffield, England, a brother and sister set out to solve a mystery, boldly believing that the air-raid signals are only warnings. In Dacchau, Germany, two friends are brought face to face with 'the enemy' in the form of a small Polish girl - is this really who their country is fighting against? But when bombs falling on Sheffield become a reality, and the German boys are given more experience of flying in a fighter plane than they'd bargained for, the children's adventures swiftly become a terrifying fight for survival.