Director Credit, also known as Duke Red, is a wealthy and influential U.S. statesman and the primary financier of the Marine Express project. He habitually claims credit for the inventions of others, particularly Dr. Nazenkopf. Credit's motivation is to leverage the Marine Express maiden voyage to enhance his political and financial stature, intending to present its success as his personal achievement upon arrival in Japan. He boards the train with his daughter, Milly, unaware she is a robot created by Nazenkopf.

During the journey, Credit confronts Nazenkopf over the scientist's objections to the train's environmental and cultural impact. This confrontation escalates into a physical altercation at a Polynesian stop, where Credit summons CIA agents to arrest Nazenkopf, leaving the scientist with a critical head injury. In the climax, Director Credit is killed during the conflict with Adam, Nazenkopf's robotic son, who temporarily seizes control of the train to destroy it.