A Russian ballerina in Vienna tries to flee KGB agents and defect.

In 1945, in the aftermath of World War II, British Col. Michael "Hooky" Nicobar is transferred from Rome to Vienna, a city divided into four governing zones: American, British, French and Russian. Hooky's assignment will be to assist Brigadier C. M. V. Catlock in monitoring possible subversive activities against the Allied nations. Accompanying Michael on the trip are his aides, Audrey Quail, Major John "Twingo" McPhimister and Private David Moonlight. Soon after arriving in Vienna, Hooky learns that he will be in charge of efforts to forcibly repatriate Soviet citizens living in the British zone. The assignment troubles Hooky, who immediately expresses his concerns about the motives of the Russians and their history of poor cooperation. After receiving their orders, Hooky, Audrey, Twingo and David are sent to a convent, where they will living during their stay in Vienna. There, Twingo meets a beautiful but mysterious dancer who calls herself Maria Buhlen, but whose real name is Olga Alexandrova. Maria, who is a Russian, conceals her identity from all but the Mother Superior at the convent, fearing that the revelation will result in her deportation to Russia. Twingo falls instantly in love with Maria, but she goes to great lengths to avoid him because she does not know if he can be trusted. Determined to win Maria's attentions, Twingo attends her ballet rehearsals night after night, but does not succeed in impressing her. One day, Mother Superior formally introduces Maria to Twingo, and they make a dinner date. During their dinner, Maria tells Twingo that she is not Austrian but does not reveal her nationality. Later that night, after leaving her apartment, Twingo sees a mysterious figure lurking near her building. The next day, when Catlock tells Hooky that the Russians are looking for a woman named Olga Alexandrova, he begins to suspect that the woman he knows as Maria is really Olga. Maria eventually tells Hooky about herself, that she is the daughter of Russian dissidents, and confesses that she is very frightened. After learning that the Mother Superior is providing sanctuary for Maria, Hooky is faced with the dilemma of dutifully reporting her to the authorities or protecting her from harm. When Russian Colonel Piniev and his aides arrive at the convent looking for Maria, Hooky does not reveal what he knows. After the Russians leave, however, Hooky tells Maria that he plans to turn her over the following day, and puts Twingo in charge of guarding her. Twingo gives Maria the key to the convent, thus allowing her to flee unnoticed late in the night. The plan is foiled, however, when Hooky catches Twingo aiding Maria. Later, when Piniev returns to the convent and assures Hooky that Maria will be treated well, he surrenders her to the Russians. Twingo is angered by the betrayal, and the Mother Superior criticizes Hooky for his action. Several days pass, and Hooky and Twingo continue their repatriation assignment with a visit to Russian Professor Serge Bruloff. When they inform Bruloff that he is being deported, Bruloff, rather than face a return to Russia, shoots himself in the head. The incident causes Hooky to question the Russians' treatment of their citizens, and he when he sees Maria crying out to him from the back of a deportation truck, he changes his opinion of the repatriation efforts and vows to raise an international awareness of the Russian policy. One day, Hooky takes Mother Superior with him to inspect a train carrying displaced persons, and they are shocked when they see the deplorable conditions on the train. Mother Superior blames the Russians' cruelty on their lack of faith in God, and after the inspection, she tells Hooky that she saw Maria on the train, and that she must have escaped from the convoy taking her back to Moscow. When Hooky learns that Maria and the other displaced persons are being sent to a remote British zone in southern Austria, sends for her and reunites her with Twingo. The next time Piniev visits the convent looking for Maria, Hooky refuses to cooperate with him. The next day, Hooky meets his superiors and learns that a brief he wrote about forcible repatriation is being considered by the United Nations, and that the British and French have vowed to end the policy. Because of his unyielding stance on the issue, Hooky is relieved of his duties. Tragedy strikes a short time later, when Maria, discovered by the military police, kills herself by jumping out of a window. Time passes, and Hooky's efforts to end repatriation finally succeed. After receiving word from his superiors that the army is to be "humanized," he is promoted and put in charge of administering the new policy.