 US 24, an American Navy base in a small island in the Pacific, is annihilated. Hubert Bonisseur de la Bath, a French aristocrat that is also a secret agent, OSS 117, is sent to Tokyo to investigate who did it. Soon, he finds out that a cypher girl in the American embassy had passed vital information to a Japanese gang. Eva Davidson confesses to him that she did that under cohertion, and is now ready to cooperate. OSS 117 will pretend to be Eva s husband, to better cover the contacts between her and the gang that is pursuing more information about a second naval base. Each step is a battle for his life, and he suspects that Eva may have not tell the whole truth.