In 1940, as the German Army approaches Paris, diplomat Andre de Mornay and his American wife Kitty have a heated argument about her supposed infidelities. The impetuous, somewhat frivolous Kitty denies Andre's charges, then announces she is moving in with her former governess, Englishwoman Emmyline Quayle. By the time Kitty drives up to Emmy's rooming house, however, Emmy is frantically preparing to leave Paris. At first, Kitty refuses to believe that Paris is about to fall, but when she learns that the American embassy is deserted, she joins Emmy in flight. The women are soon trapped in a sea of cars and pedestrians, all trying to flee the city. Kitty avoids the jam by turning onto a side road, but the road soon ends at a German barricade. Although the German officer orders her to return to Paris, Kitty insists on stopping at an inn run by an old friend, Papa Renard. Once he recognizes Kitty, Papa nervously invites her and Emmy inside, then confesses that he is hiding a downed British pilot named Lt. William Gray. The resourceful Kitty offers to help Gray elude the Germans by hiding him in the back of her car and driving him to Paris, where she hopes her diplomatic friends will further aid him. On the way, one of Kitty's tires blows, and a German patrol, led by Capt. Kurt von Weber, happens by. Attracted to Kitty, von Weber insists on changing the tire and escorts her back to Emmy's rooming house. Once the Germans have departed, Kitty and Emmy sneak Gray past Mme. Martin, the concierge, and hide him in Emmy's flat. Seven days later, Gray is still at the rooming house, as Kitty has had no luck securing help. Aware that the Germans will kill anyone who is caught aiding the enemy, Gray announces he is leaving. Just then, however, the Gestapo storm the building and demand to search Emmy's place. Kitty hides Gray in the fireplace, and when the unsuspecting von Weber shows up with flowers for her, the Gestapo leave empty-handed. Fearful that Emmy's obvious nervousness will make von Weber suspicious, Kitty then suggests that he go dancing with her at a popular night spot. By chance, Andre is dining at the same place and, while dancing with his estranged wife, learns about her predicament. Andre pledges his help, and the next day, he arranges to have Kitty, Emmy and Gray smuggled into free France. However, just before they are to leave with their contact, greedy baker Tissier, Emmy is picked up for questioning by the Gestapo. Although Kitty and Gray cross safely, Kitty, who had promised Andre she would return to America, insists on going back for Emmy. Back at the bakery, Kitty and Emmy reunite and then head back to Paris. Sometime later, Kitty hears about a classified advertisement through which refugees can exchange coded messages with one another and sends a coded invitation to stranded pilots suggesting they contact her. In response, Kitty receives three letters, including one from a Father Dominique. After Kitty and Emmy question the priest and are convinced that he is genuine, he takes them to his church's secret basement, where he has hidden a large group of Allied servicemen. By drawing lots, two soldiers are selected for escape and hide in Kitty's car. Upon arriving at Tissier's, however, they learn that the baker has been shot. Kitty eventually comes up with a plan to smuggle the men into a funeral procession, knowing that the town's only cemetery is across the river in free France. With help from the local undertaker, Kitty's scheme succeeds. Instead of fleeing with the soldiers, Kitty and Emmy decide to return to Paris and continue their work with the underground. Two years later, the Germans have grown frustrated at their inability to capture enemy pilots, and arrange for a German spy to pose as an downed English pilot in order to expose the underground. The spy, who calls himself Lt. Commander Stowe, is delivered to Emmy's antique shop through the usual escape network, but Emmy becomes suspicious of him when he refers to scones as coffee cake. At that moment, she receives a frantic phone call informing her that Stowe is a spy. Stowe deduces his cover has been blown and calls Gestapo headquarters. Desperate, Emmy hits a startled Stowe over the head with a candlestick, killing him. Emmy then races to her rooming house to warn Kitty, but before the women and Andre, who has rejoined them, can flee the building, von Weber and his men storm in. Kitty and Andre manage to escape to the cellar, where they hide among the furnace coal, but Emmy is caught. The vindictive von Weber, who is unaware of Andre's presence, refuses to leave until Kitty is caught and, fearing for Emmy's safety, Kitty finally knocks Andre out and gives herself up. Two years later, after the liberation of Paris, Emmy and Kitty are released from their prisons and tearfully reunite. For their heroic deeds, the French government awards them medals, which are pinned on them by a proud Andre.