At the height of World War I, the German ace aviator, Captain von Rauffenstein, shoots down the plane of the aristocratic French pilot, Captain de Boeldieu, and his co-pilot, the working-class civilian mechanic, Lieutenant Maréchal, during an air-reconnaissance mission. As the captured officers find themselves in the Hallbach POW camp for officers, they befriend the wealthy former Jewish banker, Lieutenant Rosenthal, and along with a handful of determined compatriots, they organise an escape. However, fate has other plans in store for them, and shortly before the implementation of the plan, they are transferred by train to the impregnable Wintersborn fortress-prison in Alsace, France, overseen by Rauffenstein himself. More and more, respect and appreciation bond von Rauffenstein and de Boeldieu. But, will this delicate relationship, and the grand illusion, stand in the way of breaking out?