Corporate executive Carl Schaffner is a German-born British industrialist in New York on business. After he gets word that Scotland Yard is investigating a $3,000,000 embezzlement he has committed, the imperious, mean-spirited Schaffner thinks he has sufficient time to take an inconspicuous train to Mexico where he can escape extradition. He miscalculates, and his crime has become headline news before he can cross the border. He drugs and switches identities with fellow train passenger Paul Scarff, who looks like him and has a Mexican passport. He throws him off the train but later discovers that Scarff is wanted in Mexico as a political assassin. Schaffner must double back and track down Scarff to get his original passport back. He allows himself to be taken to Mexico as Scarff, where he declares his true identity to local police because as Schaffner he is not wanted there. The local police chief and Scotland Yard inspector Hadden conspire to keep him trapped in the Mexican border town of Katrina in an effort to get him to cross the bridge back into the U.S. and face justice. The misanthropic Schaffner has grown attached to Scarff's pet spaniel and is tricked into going across the dividing line of the bridge to get the dog. He is accidentally killed trying to escape the authorities. The final irony is that the discovery his own humanity has cost the cynical, friendless Schaffner his life.