Three children strike a deep friendship after a chance encounter during World War 2.
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.
Rumsza, the elderly railwayman, leading a sedate life with his wife, misses his only remaining son (two older boys were killed in the war). Joziuk finally returns from the military in the first scene but with the pregnant Zosia, while Rumsza expected him to marry Celinka, the daughter of Krywka, his only friend and neighbour. The hero will not accept the new situation; he throws his son and Zosia out of his house. Celinka is distressed but she still harbours hope for Joziuk. The birth of the child changes the situation: Rumsza accepts his son's relationship but Celinka decides to leave.
A man has been found dead after having been hurled from a train. As security agents, police and a medical examiner piece together his identity, three accounts emerge: one set during World War II, one in the immediate aftermath of the war, and one in contemporary Poland.