Saro Franzese is twenty years old and has been called to do his military service. He is assigned to the 14th battalion of helicopter-transported assault infantry, an elite, highly specialized unit. He is an open boy and finds everything he experiences to be a great game. For him the drills, the helicopters and the whole military environment itself is amusing.

Drill sergeant Gianni Tricario soon becomes his best friend, but when Tricario reveals his homosexuality, Saro runs off in shock, accepting a ride from the first car that comes along. That ride is just the beginning of a terrible spiral of events in which he is violently overpowered by a secret faction of the military establishment led by Captain Silvio Roatta, a brilliant officer and true Spartan, vices and virtues included. From that moment on, in order to obtain justice, Saro leads a difficult fight. He must confront the civil and military institutions deployed in defense of Captain Roatta, but within these same institutions he also finds the people who will stay by him and help him to pursue a battle which seems lost from the start. A dark and disturbing film, Marching Into Darkness shows one possible result of a "don't ask, don't tell" approach to homosexuality in the military.