Commissioner Lohmann is already planning his holidays. An unexpected phone call calls him back to work. A member of Interpol was murdered. The head of an organisation wants to come into contact with the gangster organisation of chicago. But who is this? Mysterious murders happen and all trails lead to a penitentiary. But there is Joe Como, FBI agent, who is helping commissioner Lohmann. But soon Lohmann doubts Comos' identity. When Lohmann sees the name of Dr. Mabuse mentioned in a book found by a victim he believes that Dr. Mabuse is the mind behind the crimes...