In a futuristic city sharply divided between the rich and the poor, the son of the city's mastermind meets a prophet who predicts the coming of a savior to mediate their differences.

After a detective is assaulted by thugs and placed in an asylum run by Professor Baum, he observes the professor's preoccupation with another patient, the criminal genius Dr. Mabuse the hypnotist. When Mabuse's notes are found to be connected with a rash of recent crimes, Commissioner Lohmann must determine how Mabuse is communicating with the criminals, despite conflicting reports on the doctor's whereabouts, and capture him for good.