The film depicts the efforts of French railway workers of the Chalon-sur-Saone region who supported the activities of the Resistance during the Nazi occupation in World War II. It consists of two halves: the first part appears like a documentary showing the railway workers` secret war methods, the smuggling of men, material, and information ending with the execution of Resistance members, whilst the second half resembles more a conventional war film as it tells the story of how German convoy „Apfelkern“ sabotaged.