After staging a successful bombing raid on Tokyo, pilot Steve Ross returns to San Francisco, where he reminisces about his lost love, army nurse Abby Drake, who he believes perished while on duty in Bataan. Steve's leave is curtailed when he is ordered to report to Washington and asked to volunteer for a special mission. Because Steve was reared in Japan and is fluent in the language, the army proposes that he undergo plastic surgery to become a "Japanese" so that he can infiltrate the army and contact scientist Louis Jardine, a prisoner of war who possesses the formula to build an atom bomb. Steve accepts the mission and after the surgery is sent to a city near Hong Kong, where he becomes known as Sergeant Takishima, a Japanese soldier who is being shipped back to Japan after being discharged for battle shock. As Steve's ship nears Tokyo, he jumps overboard and, after swimming ashore, walks to the Kamuri concentration camp, where Jardine is being held prisoner. At the camp, Steve is assigned to work at the supply depot and there meets Haan-Soo, a Korean errand boy who is a member of the underground working with the U. S. When Haan-Soo tells Steve that Jardine has been hospitalized with black fever, Steve gets himself reassigned to the hospital by bribing Major Nogiea, the medical director who has been pilfering hospital supplies. Steve's assignment must be approved by Colonel Eco Okunura, the perceptive camp commander, who was also Steve's college roommate. Okunura fails to recognize his old roommate, but is certain that he has met the new soldier somewhere before. At the supply room, Steve encounters Abby, who has been captured by the Japanese and assigned the position of head nurse at the hospital. When Jardine, who has been working at the munitions plant, returns to the hospital that night, Steve contacts him. At first Jardine doubts that the Japanese soldier is really an American agent, but Steve convinces him. Soon after, Okunura makes an advance toward Abby, and when she rejects him, he takes revenge on Nogiea, who has also tried to seduce the nurse. Accusing Nogiea of larceny, Okunura demotes him and then orders him to commit suicide. After Nogiea complies, Okunura accuses the nurses of his murder and orders Abby to report to his office. There, Okunura again tries to seduce Abby but is interrupted when Steve arrives with proof of Nogiea's suicide, thus freeing Abby to leave. Okunura orders Steve whipped for his insubordination, and as Abby tends to his wounds, she experiences confusing emotions toward him. Later, Steve confesses to Jardine that he and Abby were engaged and the pilot's wings she wears are his. Although the plan had been for Jardine to transmit the data to Steve, Steve decides that he, Abby and Jardine must all escape quickly before the tenacious Okunura uncovers his identity. An escape plan is devised for that night, but when Haan-Soo learns that Okunura has sent for Takishima's former commander to verify his identity, Jardine suggests setting an explosion at the munitions factory as a diversion. As Haan-Soo leaves for the plant, Okunura summons Abby to a party at his house. Under the ruse of delivering an officer to the party, Steve drives to the commander's house with Jardine hidden in the backseat of the car. At the house, Okunura has sequestered Abby in a room and is about to rape her when he sees Steve being chased across the lawn by a watchdog. Recognizing Steve as his old roommate by the way he sprints, Okunura exposes him to the assembled officers and is about to kill him when the munitions plant explodes, throwing Okunura and the others to the floor. After strangling Okunura, Steve rescues Abby and reveals his true identity to her. With the officers in pursuit, Steve, Abby and Jardine flee to the beach, where they are to be rescued by a boat. There, they are met by Haan-Soo, who joins Steve in holding off the soldiers while Abby and Jardine sail to safety. Steve and Haan-Soo's sacrifice allows for the development and deployment of the atomic bomb, assuring that "mankind can walk unafraid in peace with goodwill toward men."