In Vienna, 1956, after Soviet tanks crush the Hungarian uprising, American adventurer Michael Reynolds (Richard Widmark) is hired by an international espionage ring to smuggle a noted scholar and resistance leader, Professor Jansci (Walter Rilla), out of Communist-ruled Hungary during the Hungarian Revolution of 1956. Reynolds goes to Vienna to see the professor's daughter, Julia (Sonja Ziemann), and he persuades her to accompany him to Budapest. Once there, Reynolds is kidnapped by freedom fighters who take him to the professor's secret headquarters.