In May 1940 a packed train takes refugees from a French village near the Belgian border away from the advancing German forces.. On it are Julien, a short-sighted radio repairer, and his pregnant wife and daughter. The women are given priority in a carriage at the front while he has to scramble into a cattle truck at the rear. There he is struck by a mysterious and beautiful young woman on her own.
At a station, the train is split and he is separated from his wife and daughter. As his half of the train slowly continues across war-torn France, sometimes bombed and strafed by German aircraft, he and the silent woman gradually become more intimate and eventually become lovers. He learns that she is a German named Anna, that she is Jewish and that her husband was taken by the Nazis two years ago.
When the train finishes at La Rochelle, he gets her fresh papers as his wife. Then he discovers that his real wife and daughter are already there in a hospital with his newborn son. Anna quietly walks away through wolf-whistling German troops.
Three years later, back in his village with his family, Julien is called into the police station. A Jewish woman in the Resistance has been captured with false papers issued in La Rochelle in the name of his wife. He professes ignorance, but the inspector then calls the woman in. For a while the two pretend not to know each other, until Julien eventually gives her a last silent caress.