An express train from Paris to occupied postwar Germany holds French, American, German, British and Russian passengers, at least some of whom are more than they seem. A political assassination en route threatens an important conference, and beautiful Frenchwoman Lucienne recruits 4 fellow passengers of different nationalities to help find a missing man. As time runs out, the five must comb the shadowy ruins of bombed-out Frankfurt, with few clues to help them...