Florence, Italy, 1925, during the fascist dictatorship. In order to live near his girlfriend Bianca, young Mario moves to a humble street in the old city center, where he befriends Maciste and Ugo, two anti-fascists.
During the winter of 1944, the partisans stationed in the Ligurian Apennines must go to a factory in Genoa, in order to pick up a delivery of weapons. Meanwhile, there's a strike in the city and the Nazis are trying to suppress it violently. The factory becomes the scene of fighting between the Germans and the partisans but the latter, aided by the workers, will be able to get the better.
