Un agent de l'FBI s'adona que té una filtració important d'informació d'alt nivell. La responsable és la bella espia Carla. Les complicacions arriben quan tots dos s'enamoren.

Tim Hanley, an American agent, posing as a lawyer with the United States Embassy in London, and Reggie Oliver, a Scotland Yard detective, posing as a music critic are both keeping their eye on Carla Nillson, a famous singer, whom they suspect of espionage. They all meet in London, then in Lisbon, and eventually in New York City, where Carla sings on the radio.