 Near the end of World War II, the Allies must find out how much the Axis knows about building atomic bombs. The OSS recruits a physicist, Alvah Jesper, to reach his former colleague, Katerin Lodor, now in Switzerland, and bring her out for debriefing. He reaches her, but a German agent is quickly onto him, and Lodor dies. Jesper must now get into Italy, go underground with the help of Gina, a resistance leader, and convince Polda, a physicist there, to leave with him. Polda won t go until his daughter is rescued from German detention. As Jesper s pal Pinky works on rescuing Polda s daughter and as time for escape runs down, Jesper and Gina fall in love.