Double Crime in the Maginot Line (1937)

Commander D'Espignac is slain in a fortress of the Maginot Line ( a line of concrete fortifications, obstacles, and weapon installations built by France in the 1930s to deter invasion by Germany. )Captain Bruchot is the main suspect ,for he had a quarrel with the victim the day before. Bruchot,helped by superintendent Finois will unmask the killer: three officers who may be guilty and a German infiltrated the French forces.