After eight long years of Japanese aggression, the people of China are still fighting. One of the Japanese targets is the mountain village of Wan Li, which serves as a command base and supply center for the Chinese rebel leader, Chen Ta, and his guerrilla army. At the House of Mercy American Hospital in the village, Dr. Sara Durand receives a cablegram from Dr. Gray Thompson, the hospital's chief of staff, who has gone to New York to secure equipment and supplies. Sara is heartened to learn that Gray is soon to return but saddened by the news that he is bringing his bride with him. Soon after, Chen Ta brings Colonel Yasuda, a wounded Japanese officer, to the hospital for treatment. While there, Chen Ta becomes attracted to nurse Siu Mei, who cautions him that she is betrothed to Dr. Kim. After Chen Ta departs, leaving Yasuda behind in the hospital's charge, Gray and his mink-coated wife Louise, arrive. When Japanese bombers strike, Gray places Kim, a disdainful man who despises all foreigners, in charge of Yasuda and, after escorting Louise to the bomb shelter, returns to the hospital to help Sara with the casualties. Terrified by the bombs, Louise cringes in fear, while Yasuda plays on Kim's dislike of Americans to recruit him to the Japanese cause. After the attack ends, Louise returns home and Sara comes to welcome her. Louise, worried by Sara's beauty, accuses her of being in love with her husband and informs her that she plans to return to New York with him as soon as possible. When Gray enters the room and interrupts Louise's tirade, however, she feigns friendship for Sara. The air raids continue, and as Louise cowers in the shelter, Kim reassures her that the structure is secure because it houses ammunition for the guerrillas. Kim's words are overheard by Yasuda. Later that night, Louise awakens to an empty bed and hurries to the hospital, where she finds Gray and Sara and accuses them of having an affair. After she storms out of the building, Yasuda, who is aware of Kim's rivalry with Chen Ta, asks the doctor to keep him at the hospital rather than releasing him to the guerrilla leader. When Chen Ta presents Siu Mei with a bouquet of flowers, Kim decides to help Yasuda and administers medication that will make him appear ill and therefore unable to be moved. Asked by Chen Ta to treat his wounded men in the hills, Gray takes Sara and Siu Mei with him, leaving Kim in charge of the hospital. After they leave, Yasuda, who has deduced that, although Kim claims to be Korean, he is really half-Japanese, threatens to expose his ancestry unless the doctor cooperates with him. Yasuda instructs Kim to send a message in Louise's name, asking that a plane be sent to the city so that he can escape. Meanwhile, at the rebels' stronghold, Chen Ta proposes to Siu Mei, and when she responds that she is already engaged to Kim, he replies that she will never find happiness if she is unhappy in love. As Chen Ta speaks his words of wisdom to Siu Mei, Sara and Gray finally acknowledge their love for each other. Back in the village, Kim commiserates with Louise and offers to arrange for a plane to fly her home. Louise is reluctant to accept his offer until Sara returns to the hospital and chastises her for making Gray unhappy. Vowing to return home with her husband, Louise agrees to send Kim's coded request for a plane, and Little Goat, the Thompsons' servant, sees Kim hand her a slip of paper. Soon after, the bombing of the village stops. On Christmas Eve, Louise accuses Gray of showing more concern for his work than her happiness, and he reluctantly agrees to take her home. Little Goat overhears his promise and the next day at the hospital, he tells Gray and Sara about the message. Realizing that the delivery of Louise's message coincided with the cessation of the bombing, Gray goes to Yasuda's room to confront Kim. At that moment, Japanese paratroopers drop from the sky, and Kim realizes that he has been double-crossed and that Yasuda's message was not a request for a plane, but a secret code informing the Japanese about the location of the ammunition. Yasuda then shoots at the doctors and escapes, fatally wounding Kim but only grazing Gray. In the hills, Chen Ta and his men see the paratroopers and race toward the village while Thompson leads the villagers in defense of the ammunition supply. Witnessing the death and destruction that she has wrought, Louise runs out into the line of fire and is killed. After capturing Yasuda and securing the ammunition, Chen Ta promises to return for Siu Mei when peace is restored. As the air raids begin again, Sara and Gray join hands to face the bombs together.