This improbable but exciting story concerns physics professor Alvah Jesper (Gary Cooper), recruited by the OSS because of his far-reaching knowledge of atomic weaponry and sent to Italy at the end of WW II to locate Dr. Polda (Vladimir Sokoloff), an atomic scientist being held by the
Germans. En route, he meets in Switzerland with Austrian scientist Katerin Loder (Helene Thimig) who is then killed. Jesper moves on to Italy, followed by Nazi agent Ann Dawson (Marjorie Hoshelle). Once in Italy, Jesper and his associates, local partisan Gina (Lilli Palmer, in her first US film
role) and Allied agent Pinkie (Robert Alda), combine their talents to find the scientist and...