In
London during
World War II, Lieutenant David Halloran, a
United States Army Air Forces B-25 bomber pilot with the
Eighth Air Force, and Margaret Sellinger, an English nurse, meet on
Hanover Street in a chance encounter. The following day, Halloran's
squadron is sent to bomb
Rouen in
Nazi-occupied France when the plane's engine is hit, but the fire is put out. Cimino, the
bombardier, begs Halloran to let him drop the bombs early and turn back, but Halloran does not care about the danger and orders him to wait until they are over the target, prompting Cimino to angrily exclaim that he hates Halloran. Halloran and Sellinger meet again two weeks later in a secret assignation on Hanover Street and they rapidly fall in love. Although she is married and tries to resist, she is drawn to the charismatic American and they begin an affair. By contrast, her husband Paul Sellinger is, by his own description, suave and pleasant but fairly dull. A former teacher, he is now a trusted member of British
intelligence. During the next few missions, Halloran orders Cimino to drop the bombs early, as he is scared of death because he now has "a reason to live", much to the anger and disappointment of his co-pilot Hyer. Weeks later, Halloran hears something odd in the engine before take-off and turns back, forcing another pilot, Patman, to go in his place. That night, it is revealed that Patman's B-25 was hit in the
bomb bay with the bombs still on the plane, killing all on board, and that had it not been for that engine, it would have been Halloran. Ashamed of his actions, Halloran volunteers for an
undercover mission to deliver a British agent into occupied France. At the last moment, Paul Sellinger wearing a
SS officer's uniform takes the place of the agent, and himself joins the mission. His reasons are initially unclear, but he slowly reveals that he wants to prove himself in the field. The B-25 is hit by
anti-aircraft fire near
Lyon and the crew is killed except for Halloran and Sellinger, who are forced to
parachute from the aircraft. After Sellinger injures his ankle, Halloran agrees to help him with his mission to infiltrate the
Gestapo headquarters in Lyon, posing as an
SS officer and photograph an important document that lists the German
double agents in British intelligence. They take shelter in a
barn and are assisted by the farmer's daughter, a member of the
French Resistance. Sellinger is able to photograph the documents before alarm is raised when Halloran makes the incorrect response to a question in
German, but the pair manage to escape back to the farm after a lengthy
motorcycle chase. Sellinger says he was motivated to volunteer for the mission to impress his wife, who Halloran then discovers is Margaret. The farmer's daughter tells them the French Resistance has prepared to help them escape from France. However, the farmer reports them to the Germans who then surround the barn, but they successfully escape again when they are assisted by the French Resistance, though Sellinger is badly injured. In London, Margaret finds out that Halloran and Sellinger are together and have come back home, with her husband wounded but alive. Going to visit him in the hospital on Hanover Street, she meets Lieutenant Halloran for the last time. They embrace and kiss, and he tells her that he loves her "enough to let her go", she goes in to see her husband as he goes back out into Hanover Street, where the love story had begun. ==Cast==