Summer 1941. Over Nazi-occupied France, a Royal Air Force B17 Flying Fortress becomes lost after a mission and is shot down over Paris by German flak. The crew parachutes out over the city, where they run into and are hidden by a house painter and the grumbling conductor of the Opéra National de Paris. Involuntarily, they get themselves tangled up in the manhunt against the aviators as they help the airmen to escape to the free zone with the help of Resistance fighters and sympathisers.