The Italian soldier Giuseppe Santucci, on his way home from the Russian front has his machine gun stolen in Warsaw. Afraid of consequences, he stays in Warsaw and occupies a flat of the Polish girl Maria, whom he suspects of stealing weapon. Maria indeed is an active member of the Polish resistance, contrary to her brother, Staszek, a painter, who only wants a calm living. In a course of events Giuseppe falls in love and, along with Staszek, becomes a hero of the Polish resistance.