The stern and reserved Gustav Hartmann, known as "Iron Gustav", is the last Berlin cab driver. At the end of the 1920s, his time is over as horse-drawn cabs are replaced by automobile cabs. He is threatened with impoverishment. His family wants to have him incapacitated. So he sets off on one last great journey that takes him from Berlin to Paris and back. A reporter with a nose for a big story accompanies him, Gustav becomes famous, returns to Berlin in triumph and, having become a gentle and approachable person, reconciles with his family.