Double Crime in the Maginot Line

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 who infiltrated the French forces.