In 1940, during the Battle of France, Allied soldiers have retreated to Dunkirk. Tommy, a young British private, is the sole survivor of a German ambush. At the beach, he finds thousands of troops awaiting evacuation and meets Gibson, who is burying a body. After a Luftwaffe dive-bomber attack, they find a wounded man. They rush his stretcher onto a hospital ship, hoping to get aboard, but are ordered off. The ship is sunk by dive bombers; Tommy meets Alex. They leave at night on a destroyer, but it is torpedoed by a U-boat. Gibson saves Tommy and Alex from the sinking ship, and they get back to the beach.