"Case Closed" by Arthur D. Hemmings begins in May 1937 with Otto Schmidt, a German exile in Paris, committing a bank robbery and killing a teller. This act sets in motion a chain of events involving his accomplice Helmut and the French police, particularly Inspector Renau. Otto and Helmut attempt to flee, eventually agreeing to meet in Innsbruck, Austria. However, their escape is complicated by their connections to German intelligence, as they are revealed to be agents, Rainer (Otto) and Lutze (Helmut), who disobeyed orders.

The Abwehr, upon learning of Rainer's crime, initiates a search for him to prevent his capture by the French. Meanwhile, Inspector Renau investigates the bank robbery and, later, the murders of Monsieur and Madam Durand, eventually linking them to Otto Schmidt. The narrative follows both Otto's attempts to evade capture and the Abwehr's efforts to control the situation alongside Inspector Renau's determined investigation. The book appears to weave together elements of crime thriller and espionage, set against the backdrop of pre-war Europe. The initial focus on a bank robbery and murder expands to involve intelligence agencies and their clandestine operations.