In September 1944, Teuntje Visser works in the office of a collaborationist mayor in German-occupied Zeeland as the Allies approach from Belgium.

Meanwhile, Marinus van Staveren, a Dutch volunteer in the Waffen-SS Division Das Reich, is reassigned from the Eastern Front to serve as secretary and translator for the German commandant in Zeeland, Oberst Berghof.

Marinus grows increasingly disillusioned with the Nazis' heavy-handed tactics including the execution of civilian hostages.

She and her best friend, a Resistance member named Janna, are tasked with smuggling Dirk's photographs and the map to the Allied forces advancing on Walcheren island.

Elsewhere, Glider Pilot Regiment Sergeant Will Sinclair, Lieutenant Tony Turner, and Free Dutch Forces soldier Henk Sneijder crash-land in a flooded estuary in Zeeland after their Airspeed Horsa glider is hit by anti-aircraft fire during Operation Market Garden.

After wading through the marshes, they shelter at a farmhouse whose owner informs them that Operation Market Garden has failed and that the Canadian Army have entered Holland.

Henk, exhausted and unable to swim, is left behind by Sinclair, who reaches the Allied line and joins Canadian forces advancing on Walcheren Island.

Prior to the Battle of Walcheren Causeway, Teuntje is captured while helping Janna escape on a boat with Dirk's photos and the map.

Marinus takes part in the German defense of Walcheren Island while Sinclair participates in the Allied assault.

Principal photography began in Lithuania where a large part of the movie was filmed and continued in the Netherlands and in Belgium.